Baxi boiler problems

[Seadoogsx1221]

Please bare with me I'm not too technical. Recently moved into new house with a baxi bermuda inset 2 50/4 E and a Micrgyr RWB20 controller. The problem I have is that our hot water is extremely hot, and the boiler seems to be firing every 6-7 minutes for about 30-40 seconds as if it's trying to keep the HW topped up. I have replaced the stat on the outside of the tank in the airing cupboard as this seemed to be turning and turning. Having left it over night the stat is clicking at nearly 80degrees so I guess the water temp is still very hot. It does not seem to have stopped the boiler firing still every few minutes.

The other issue I have is that on the controller if I switch both off boiler does nothing
If I switch on HW on its own only the HW indicator turns from blue to red indicating its on again
But if leave HW off and switch CH on then both HW and CH indicators come on. Does this mean I can't have just CH on?

Question; should the boiler be firing every few minutes for a short time?
Should the new stat have stopped the hot water heating up and calling for heat if that's what's happening?
Is it worth emptying hot tank allowing it to start again and set the stat to say 50degrees and see if it stops then???

Any help gratefully received. Thanks

 

[45yearsagasman]

Vee ask de questions. Please detail ALL your system controls, and that includes motorised valves etc.