I said yesterday that the room stat might be OK and that it was me that was feeling cold due to a long bout of chest problems.
When I went to bed last night, the dining room temp was 71.9 F. This morning it was 70.1 F. The sun rises at the front of the house, so that would have made little difference at the back where the dining room is. All this was before the timer allowed the boiler to switch on. So, it is no wonder that the thermostat was not making the rads put heat out. I am thinking of doing what another poster said earlier and reducing the room stat by a fraction of a degree every three days or so.
Many thanks to all who answered my original post.
Dave