Thanks. I've ordered some arctic silver from wootware, but picked up some regular silicone-based stuff (unick) from communica in the meantime. There's definitely something wrong tho - Realtemp reports a 100+ temp right after booting after being off for 20 minutes. As soon as I do any graphic-heavy work, it crashes.
Sorry to go a bit o/t - but if anyone knows any good repair centres in cpt (out of warranty pc) I'd really appreciate it. I've used the one in Montague Gardens before - think it's computer mania? Not sure how they stack up to other places, but some options would be nice.