Dear Tony Glazier......Thanks for letting me know that there is probably nothing wrong with my system. I am still getting used to it, at least now I can rest easier. Many, many thanks for your reply and sorry for not replying sooner.
André
I have a potterton profile 80e which supplies 12 radiators via a Grundfos pump. There is a hot water cylinder which is vented.
I am not sure if the system is working properly ( recently moved in ) when the heating is switched on all the radiators heat up but fine but once the hot water comes...