[blueblock]

Well, I've had the car back from the shop two days now and it's gradually settling back down to normal - second gear is coming in quicker on cold starts and first gear is there again when I stop.
The fella at the garage told me it looked like the box had never been serviced before (why don't people look after their cars?!!!!) and the amount of gunk in it was probably affecting the operation of the governor, so in the end I'm glad I bit the bullet and had it professionally done - well worth it to have it properly cleaned and the filter and gasket done too. Now I just need to fix my overdrive relay...