Baxi / radiators are hot when the heating switch set off ?

what area are you in

halls heating & gas services
May 2011

is DHW temperature noticeably lower than normal?
then probably divertor seized & stiff

you could try isolating the CH valves to see if DHW temperature increases to confirm above diagnosis

divertor valve might only need stripping, cleaning & regreasing to fix problem

worst case scenario
replace divertor valve

manwithnoname
May 2011