Thanks for all your replies, I'm pretty much in agreement with you!
Sparky, I also have noted the SE7A box appears more readily available, but I now think it's for the Hybrid Jazz, so won't buy it. The car is currently with an auto transmission specialist who (says he) is very familiar with the cvt, and has quoted the prices I mentioned. This is after his £90 'diagnosis' already carried out. Those are his prices; he says he would replace all the bearings in the box, not sure how many that is, about 8-10? It's take it or leave it, I just have to decide whether to take it . . . There aren't any other specialists, Honda or otherwise, in my area, and I'n not keen to drive 80 odd miles to the next nearest.
VicW, my car must be just post I-shift (March 2011), and therefore with the torque convertor - thanks.
OldUser, there's no doubt the gearbox is the problem. The noise is serious, the Honda main dealer said he wouldn't drive the car one mile!
I think I'm stuck with the current specialist, can't find a s/h replacement, and have run out of options, Thanks all of you.