Combi boiler heating switched off but rads warm?

Just had a new combi boiler fitted .........when the heating is switched off the radiators are warm !!!!! They fluctuate.....by this i mean they get quite warm then go quite cool almost like the TRV's are working but the heating on my controls is switched off?

Anyone have any ideas please? I hve read about this happening on other systems eg thise with hot water tanks but cant find anything on it happening on a combi boiler.

The mad thing is the boiler isnt firing up to be able to heat the rads so where is this hot water in the rads coming from.

There are no outside pipework and nowhere where the water int he pipes could be getting heat from.

Any help appreciated