I have a bit of a stupid question
I have been trying all year to increase the speed of tonguing on repeated notes and yesterday it finally clicked. I immediately decided to put my new found skill into practical application in a piece which has seven semi-demi quavers on the same note only to discover that I don't know how to count them. If I count "one, two, three, four etc." in my head this slows the tonguing down too much. If I just play fast notes for one beat I don't really know how many I've played.

I'm sure there's some obvious answer that I can't come up with myself

How about saying semiquaver, semiquaver to yourself. Will that work?

I'll try tomorrow and let you know.

Having just tried tonguing (without a reed) and saying semiquaver in my head I think my problem is that my tonguing is not yet good enough not to have to think "t-t-t". When I count the "th" of "three" interfers with the "t". The word "semiquaver" doesn't appear to have any effect on the "t". (Not at all sure that what I'm saying is clear ).

Are you trying double tongueing or single tongueing? Just that when you say 't-t-t' I think of single tongueing. It might be a good idea to begin learning double tongueing which would make what you are trying to do much easier in the long run. I remember playing the Mozart Flute concerto in D 1st Mvt using only single tongueing for my grade 8. I recently tried this piece again for a bit of fun and realised how much easier it was using double tongueing.

You also need to think about sub-dividing the beat. First think of crotchet beats and tongue them several times. Then think of quaver beats and tongue twice in the time of the crotchet (I can't explain this very well but you get the idea i'm sure), then go on to semiquaver beats etc.

It is single tonguing - I am playing the oboe not the flute and I think double tonguing is easier on the flute. I have started learning double tonguing but it is not particularly effective yet (to say the least).