HE CB33 Boiler clock losing time?

could be the mechanical clock failing/failed. You may have some luck on the Internet searching for a spare. Here's one possible place you could try to contact (rather than search) http://www.alphaboilerparts.co.uk.

Looking at the manual, the closk on that boiler is an option anyway so your friendly engineer should be abole to connect a normal single channel central heating timeclock / programmer which you could mount somewhere convenient. (And maybe a room thermostat or combo clock/stat?)

There are even wireless ones available

If you've not got one, the manual is here: http://www.alpha-innovation.co.uk/custom/upload/instructions/Old%20models/HE%20CB%20Inst%20&%20Serv%20Inst%207%2005.pdf

Kelvin
November 2014