Coswurv, should have mentioned that it's had a brand new stat at the end of last year - this made no difference...

The coolant isn't as clean as it used to be, there's a bit of scum floating on the top now, would always stay as clean as a whistle before.

I can appreciate it's going to produce more heat now, but I would imagine the std cooling system would take it in its stride TBH?

This is why I'm thinking about just doing the headgasket, hoping that I won't need a skim as it's never properly overheated...