Finally got chance to have a proper look under it tonight. Oh dear. I'd missed a huge gaping tear in the inner CV boot on the passenger side shaft. Doh (I foolishly went to Cumbria in it yesterday - 400 miles)
So, as a desperate measure i've cleaned it out, got hold of a "universal split boot repair" kit from Halfrauds (only place open). And then I realised that the inner CV body ISN'T round is it.
So, what to do? As luck would have it I discovered that the replacement boot was big enough to go over the old one. So I cut the inboard end off the old boot and refitted it with a cable tie, to the back of it's "groove". Then I repacked the joint, inside the cup, sealed up the new boot around the shaft, let the glue dry, ran a bead of superglue all round the outside of the "old" outer boot end, slid the new one over and cable tied it on (ringed on pic). There's a rounded ridge on what's left of the old one that the new boot has gone past and it feels pretty solid now.
The small end needed the smallest section trimming off and the ridge left inside cutting back. That's cable tied to the shaft now and it all seems OK, fit wise. The shaft has a tiny bit of up/down play in it but really doesn't feel too bad. I'll test drive it later but obviously i'm expecting to need a new inner CV joint before too long....
SO, the main thing I need to ask is: Where do I go for an inner CV when I need it and does anyone know how much they are? Also can I order one in without having to take the car off the road, cos I can't take any time off work right now!!