Thanks guys,
Still waiting on verdict from cam-cover lift - now bracing myself for the worst! I'll post results.

Thinking about possible causes:
Forgot to mention in original post that someone had removed aux fan fuse (replaced). The rad fan always turned fairly quickly before and after fuse (unlike my old magno-clutch 190) but got the ok from mechanic.
Again, unlike old 190, the temp gauge never reached heights where fan would click in properly (it stayed just under/over 80C) - so I just forgot about it.
Now I'm thinking these were signs of an overheating problem - no coolant burn, no temp gauge in red, no excessive oil consumption - must be trouble