In a few weeks I will find myself in London for a day with no instrument. I could go to one or other of the various tourist traps (in November?) . . . OR I could hire a practice room. There is a piano retailer on the Edgeware road which has practice rooms for hire (£4 per hour for an upright, £7 for a grand). I'm probably going to hire a room with a grand for a 3 hour stint, but whether I do or not I wondered if anyone had any experience of this: Are the rooms sound-proofed? Will the other users be professionals? Any comments??

Only one day? Why not go to a concert instead? It seems a shame to miss out on a good opportunity to hear something interesting rather than to just do what you could do at home. I am sure that the thought of a really good grand is tempting though.

I play duets with a friend and we go to various practice rooms, depending on where'a available as we make the plan at fairly short notice - 2 or 3 days. i Steinway has practice rooms below its showroom in Marylebone Lane. My friend organises it and says he gets them for free. I presume he is telling the truth, but I don't like to query it - looking a gift horse in the mouth etc. Anyway there are several practice pianos there, all fine, though rather 'bright'. ( It's good fun trying out the pianos in the showroom - I completely fell in love with one but at £72,000, I'm afraid it's unrequited love!)
The Steinway practice rooms' soundproofing is muffling rather than complete soundproofing - you can hear the person next door but it didn't intrude - at least, we didn't find it intrusive.

There's a practice room at Knightsbridge Pianos which despite its name is in South Ken. That's £10 an hour.
I'm not sure if it's soundproofed - in fact I think there's only one practice room, but I could be wrong. Anyway, it was just us when we went.

I've also played on the grand pianos in the Edgeware road which are fine, but again rather bright.

As regards the other users, they seem to vary. Once, at Steinway, one of the rooms was being used to give a lesson (complete with pushy parents in attendance - Mum AND Dad).
I've hears some pretty impressive stuff thundering forth so presumably most are professionals - or at least extremely competent amateurs.

If I come across any others I'll let you know.

http://www.allinlondon.co.uk/directory/1123/9598.php

There are seven studios available to hire at Marylebone Lane Music Studios, link above. I don't know what the price per hour is tho, but worth giving them a call.