For anyone else with the same problem as me, here is what happened!
Well, I bought some flow switches online and got them today.
Changed both (found alot of debris in central heating flow switch - switch was not right when I bench tested it!).
Surprise surpise the system works again...
I wonder if anyone can help!?
I have a problem with my Baxi Bahama 100 combi boiler. The problem was intermittent and now seems to be a permanent issue. When I turn on the hot water everything seems to work, the gas comes on (looks like a reasonable flame) and I start getting hot water...