New to 'condenser' gas boiler - help please

[moggie 939]

Hello
I am a pensioner and have for the first time got a condenser? gas boiler in my rented flat. It is a Worcester 26 DCI and it has been set up by the engineer and I have rad heat and hot water no problem. There is just one thing I do not understand.
In the hallway I have on the wall a Honeywll Thermostat. Now, when I set it to about 23c the boiler cuts in. First there is one red light on left and then the flame kight on right cut in and the rads heat up. So far, so good. If I leave thermostat on that setting the flame light on right it cuts on and off about every 2 mons which seems a lot of times - however, everything works perfectly! When the flame light is not on there is just the light on left which seems to be the standby light. Now, if I turn the t/stat down a couple of degrees to say 20C because the rooms are too hot, then however long I wait and even if rads get cold, it will not automatically switch back on and I have ti turn it manually on tstat back to 23C!!

I have the CH on boiler set to 3 and have tried turning it up to 3+ and down to 2+ but there is no difference and no discernable change in radiator heat. Th hot water work perfectly.

Am I doing something wrong here.? Why will it not click on at say 20C and should a condensor boiler reignite every 2 minutes to keep rads hot?

Any assistance is welcome.

Thanks

Moggie