I've been looking at every single visible piece of solder on the board and have seen no cracking or solder that looks like its heated and cooled (I'd expect a slightly less perfect shape if that had happened, because the PS3 is kept vertical at all times)
I've not taken the IHS off of the RSX get though, so I'll check that later.
Gave myself a shot at repairing the damage I did to the CPU.. it's as good as it's going to get now:
Repasted the IHS too, so it's all ready to go back together. There's a little bit of paste on some of the parts - but it's a non-conductive paste.
I'll plug the HDD back into my computer to format it and recover the saved game for GT5 (pretty sure someone made a HDD decrypter right?) If not I'll just format it; once that's done I'll put the main parts back together and see whether there's any joy.