my first thought was the frost stat was firing the boiler but usually an external frost stat is only fitted if the boiler is in an outhouse or garage, many boilers have a built in frost stat but again this probably isn't going to activate unless the boiler was in an outhouse, garage etc. even if it did the boiler only fires for a short period to protect the boiler itself, i wouldn't expect the radiators to heat up much.
I am thinking that either the programmer is faulty or you haven't set it properly. some programmers can have as many as 16 on-off periods and it could be that even though you have timed the heating to go off at 10pm there could be other times still present in the programmers settings.
check the programmer to see what times are set, if thats not the answer call a heating engineer