Ferroli Modena 80E Hot water but no CH?

Hi,

I've not used my CH for a few months over the summer, went to put it on a few weeks ago during a cold spell and nothing worked. Checked the manual and it says that it may be a fault with the clock etc. I've checked all the timer/settings and they seem fine (haven't opened it up yet though).

I've checked a number of forums but can't seem to find the answer. Had a plumber over today and he said it could be the heat exchanger(!)... this would be a bit odd as the hot water is fine and the CH outflow pipe seems to be hot up until the tap (sorry don't know the technical term) which is just underneath the boiler (each of the in flow and outflow pipes has a 'tap' just underneath the boiler)

Any help would really be apprecaited!

Cheers,

Jake