Baxi Bahama 100..No hot water but there is central heating?

Baxi Bahama 100..No hot water but there is central heating?? (it seems that the central heating is working fine)

In addition to that, When the Heating is running, the pressure rises consitently until it reaches 3 bars and I turn it off. When it all cools down, the pressure returns to about 1.2 in the green.Also, I should point out that this only happens when the heating is running. There is no pressure movement when the boiler is dorment, and the hot water feature works fine (with a little pressure drop whilst on).