Thanks Lee.
Yes, in the past I've taken whole the binnacle apart - steering wheel off etc. and got in there OK to have a go with some switch cleaner.
It's always a bit more involved than you expect - I missed an England world cup game last time I did this (that must have been in 2006!).
I was hoping that there might be a quick way in - sadly it seems not. This sounds almost as fiddly as getting the whole binnacle apart - for the 1st time at least and with a risk of some 20-year-old plastic going *snap*.
Curiously, I usually find that if the speedo's being naughty flicking the rear demister on then off brings it back. Got that tip from someone (Mr Dell, I think) on here.
Thanks very much for the details, though. Maybe I prised these out from the inside - i.e. when I've got the binnacle apart - that might things easier next time.