Could not for the life of me find any processes causing the issue, so went back to basics. Remembered a youtube vid of dissembly and cleaning of said fans.
So set up my new magnifier with LED lights and opened the case. Removed the fans in line with the guidance, grabbed my fave makeup brush (!) and thoroughly cleaned fans and area around, including vents & pipework to CPU (yes really...makes and Exige airbox look ordinary!).
Reinstalled and hey presto, silent operation with occasional fan action.
Just thought I'd share!
Epilogue:
When I restarted the machine, with fingers tightly crossed, it booted OK but the clock was wrong and some tray icons didn't appear. Including networking etc. Immediate panic. Rebooted one more time. All good. Thank the Big Man. Brief brown trowser moment there
