Thanks for all the replies, much appreciated, great advice.
Alas, no Intel 320 300GB drives on ebay here (I'm in the UK). There are Intel 160GB drives but I wanted to get at least a 240GB, otherwise I'll have to rely upon cleaning some stuff off my existing drive, which will take ages.
I don't want to risk buying one from US ebay, with shipping times, potential damage in transit, extra import taxes etc...
From what I can see, all the main SSD manufacturers seem to have cloning software (similar to Intel Toolbox?), so I'm hoping that if I buy, say, a Seagate drive, then I should be OK as they have Seagate DiscWizard. Any thoughts on that?
Also, by buying a new one, at least I'm covered and can send it back if I run into a problem.
So... with that in mind, I'm looking at an Adata SU650 SSD (either the 240 or 480GB). It's pretty cheap and seems to have good specs and good reviews and comes with all backup and migration software. Will it do the job?
As for running Win 10, tried that a couple of years ago and failed... I eventually worked out that it was because of compatibility issues with my graphic card (Nvidia Quadro NVS440). I'm running multiple monitors and Win 10 would only work with 1 monitor with this card, so that meant a graphics card update. That can wait until after the SSD upgrade...but that's for another discussion.