Just as I had decided to delete the air con in my car, I've almost got it working!
I managed to bypass the low pressure sensor and after fiddling about a bit, I got the compressor turning, which it's never done before.
So, it *might* just be a case of low gas. Trouble is, it was originally R12 and I have no idea if it's been converted to R134 or not.
Seeing as it's fairly close to working now, it might be cheap enough to fix it instead of ripping it all out (which is still a tempting option).
Anyone used any local air con people?