[snodvan]

Thank you Gentlemen. All sorted

During my business like I learned (the hard way) that it is always best to "separate the variables" ie when doing/ fixing something do it in steps so you know the rogue step if all goes wrong. Therefore :

I first restored the CMOS to the original settings as per instructions provided. Actually, that seemed to do the trick ie on reboot I did not then get the "checksum bad" message.

However, for the cost of a battery (2 x CR 2032 = £4.99 from my WH Smiths but buy one get one free so effectively £1.25 each which seems pretty good) I decided to pop the old battery out and change it. Bit fiddly but done OK.

Machine now seems fine.

Interestingly the old CR2032 still measured just over 3v on a tester - but gave only 30ma on a (very quick) current check compared with couple of amps for a new battery.

Thanks again