Slight update on this BTW. I removed the cambelt to find it was just the bottom end that had seized. I removed the sump on Monday and I can't see anything wrong with it. There's a bit of carbon deposits in the sump but no metal bits. No metallic sheen to the oil either. No hot spots on the crank. What is the most likely culprit of the seizure? Should I try and crack off the main bearing caps to see if it turns over then? Or maybe the big ends I can get to. You'd think if it was a bearing fault there'd be metal bits in engine though.