Not Wanting to take over the discussion for a planned event I'd like to reply in this separate thread.
This is my own experience and other events may be affected to a greater or lesser extent.

After 5 years of building up the Adult Learners Concert in Stalybridge my figures for the last two years are very similar. I'm no statistician and statistics can be bent to prove anything so feel free to take this as you will.
Of 16 participants this year 9 were from the North West/Yorkshire and 7 from further away.
6 of those are also regulars at the South East Adult Learners event.
6 are going to be in Birmingham next week.
I had 9 forum members and 7 non forum........ 6 of the non forum members were from one teacher.
If I include Yorkshire there were only 2 'local' forum members and one of those was me.
Apart from myself there were no forum members from the Greater Manchester area. This has been fairly typical with very little take up from North West forum members or their adult students. The most I've had from the other side of the Pennines is 4....... passport control is tricky over the Pennines
As you can see my personal experience is that events elsewhere are going to have an effect on the Stalybridge concert and it would appear that at least for Stalybridge, Teddington and Birmingham there is what could be a significant crossover in terms of viability.

Some areas do seem to have a better uptake of both forum and non forum people.
Publicity wise as well as being on forum I pass the information to people I know who are in bands etc. I've had very limited success with the local press..... one problem being that around here without Ricky Hatton, Harold Shipman, a prominent councillor or Hindley and Brady you aren't going to get them to print stuff.
When they do it's not going to be accurate though I did try writing it myself but it never got in the paper. Reporters always indicate that this is an interesting venture but it would appear not to be interesting enough to print.
I get the information to as many teachers and adult students as I can (quite a number), give information to the local churches and have posters in the local music shops one of which has a music school. I've emailed the local reps of the 3 major exam boards with no response at all.
The publicity question is a little difficult as capacity is limited. This does make it difficult to decide how many extra avenues to explore each year.

Maybe this helps to illustrate why some organisers get a little jumpy over the timing of events regardless of geographical location.

I think that possibly what we've lost over the years is that distinction between those events which are 'forum events', and those which are 'events' at which forumites are welcome.

From a personal perspective, I just can't keep up with it all! There are so many events being advertised these days - something virtually every weekend - that's great, but it does get a little overwhelming. Perhaps in my lazy way I've tended to step back from all of them, rather than trying to sift though those I might want to attend.

I know myself how hard it is to get people from 'outside' to attend things which come across as being 'well-established'; there are no easy answers to that!

Something else to take into account is the amount charged by venues in the south of England (I have no experience of other areas). It seems increasingly common to add a large fee for use of piano and as much again for tuning to the hire of the premises.

Any of us hoping to organise events have to commit substantial amounts of our own money in advance. A minimum number of participants is necessary to cover costs, let alone have any left as a donation to a worthwhile cause or causes.

We haven't had a Forums concert in the south of England since the demise of Woodford (which was entirely due to the venue increasing fees beyond the point an event could be staged). We have plenty of other events such as Grand Gatherings, Adult Learners' concerts and playdays, but those, whilst enjoyable, don't allow those of us who teach to perform solos on our main instrument in front of an audience in the same way that the concerts at Woodford used to.

I'd love to arrange something like that but cannot find a suitable venue that would allow us the facilities we need for a cost of less than ?20+ a head. This is why I for one travel to venues in other parts of the country, although it's always good to catch up with Forums members from elsewhere as well.

I won't deny that there might be some crossover and I can see that Sbhoa's Adult Learner event, Blackburn and Leeds might attract similar people.

There are lots of people who aren't "adults" and who wouldn't be considered "learners" in the proper sense of the term who wouldn't be eligable to attend an Adult Learner Event. I'm not advocating that these events change their criteria.

The Eccles Playdays managed to include forum and non-forum people successfully. I think there is plenty of scope to do that but recognise it's not easy.

I also find it strange that the London based people seem to influence when we have gatherings up North but there is very little interference the opposite way. There are lots of music making activities in and around London and at times I'm envious of all the activity. Sadly other pressures on finances won't allow too many trips to the big smoke.

I'm increasingly thinking that the forum concert concept has, sadly, run its course in London and the South East. Not only do we have all the above (and the very cosy house parties taxidriver kindly hosts), there are so many other non-forum events here (off the top of my head, in 2010 there's been the East London Clarinet Choir playday, the Greenwich Early Music Festival, the regular meetings of the London Kodaly Choir and the CASS event, to name but four), and ample opportunities to meet forum people, socialise and have fun. There is the question of those of us who want to perform on our main instruments down here, yes, but really I think the way to go here now is to organise our own recitals, perform in masterclasses (eg the excellent ones at the Colchester single reed day), plus taking advantage of things like the house parties.

Since the Leeds concert is the closest event to your Stalybridge concert, both geographically and in time, I feel as if I should explain the reasons for the move of the Leeds concert to July.

As you know, the Leeds concert has always been held on the Saturday following the May Bank Holiday, a date which had to be fixed because on term-time Saturdays at the venue (a music college), classes were being held. It's a date which clashes with school and college exams, and as the concert-participating students have got nearer to their final years in education, it has become increasingly problematic for them to attend without affecting their studies. It is also very close time-wise to the events I organise for advanced players at stately homes, which this year was in late April and is likely to be around the same time next year. The clash with student exams and my stately home events led me to consider alternative dates, which the college in its new premises can now accommodate. As you know I have moved the event to mid/late July, and the reason for deciding on this particular date is because the University releases its student accommodation during the 6 week period starting in mid July, and in my opinion it is ideal for those travelling members who wish to share affordable self-catering facilities and have the same sort of atmosphere that we had when we took a cottage at Dyrham Park. If people want to use that accommodation and if there's room, I'll probably join them

As I mentioned when I announced the move of the Leeds concert to July, I realise that it is close to the Stalybridge date but there have been very few participants at Leeds who have also attended Stalybridge. As you said in your original post, only one person from Yorkshire came to Stalybridge this year, and I'm not aware that the proximity(?) (6 weeks) of the concerts was a deciding factor for Stalybridge. Nearer the time next year I will offer a choice of July dates to the intending participants and will select the date which the majority find most convenient. I hope this explains the reasons for the change of date.

With regard to the Blackburn event which inspired this thread, as you know it was not my choice not to attend Stalybridge, so I don't think it's surprising that I would like to encourage an event in Blackburn in February which I may be able to attend. It could be only a few weeks after my Leeds event but I have no problem with that.

I did have a few ideas but I haven't really got around to pursuing them yet. Not really the best of times to be running around right now, but I will post when I make some progress.

Not sure where else to put this : so here seems as good as anywhere - thanks mods for making this a fully fledged forum : it's something I've wanted for a long long time!