The Ricoh appears to be behaving itself at the moment, after I dismantled much of it to inspect the cyan toner attraction pump. I'm not convinced the problem is fully resolved, but I've spent quite a while this afternoon fine tuning the colour balance in copy mode, and it hasn't missed a beat. More time will be needed to come to a final decision.
I've a brief visit back to the UK next week, with some work involved, so I've also had to do some preparation for that over recent days. I sincerely hope that inclement weather will not disrupt my travel plans - it has a habit of doing so when I need to go back to UK during January or February!
(No picture - my camera battery is playing up!)