What is the relationship between the controls on the boiler itself, the
thermostat/programmer in the hallway and the heat in the rooms?

Our previous boiler was an Alpha CD32C and the boiler controls for both
heating and hot water were numbered from 0 to 9, and both were set to
No. 7. The thermostat/programmer in the hallway was only rarely set to
above 18C. Only on the very coldest days of winter would we have to put
it up to about 20 or 21C.

Our new boiler is a Worcester Greenstar 30i and instead of the boiler
controls being numbered 0 to 9, the readout is in actual degrees
Celcius. Both heating and HW are set to 56C but I don't know if that
was set at the factory or if the installers set it.

We are finding that 18C on the old stat/programmer in the hallway was
more than comfortable for us but the new stat/prog has to be set to at
least 20C or 21C to 'feel' as warm as it was before.

I don't know what the *actual* temp of the rooms is as we don't have a
standalone thermometer, but it's weird trying to get used to this new
system.

On top of that, and perhaps even more importantly, is the frostat.

The old Alpha boiler was up in the loft for 14 years and as far as I
know it never had a frostat connected - unless it was factory-fitted
and integral to the boiler itself but definitely no external unit was
wired in.

The new installation *does* have a (Honeywell) frostat wired in and
it's keeping the heating on all night, irrespective of if I turn the
hallway stat/programmer down to a very low level or completely off.
This is really bad in three ways:

1. Extra gas used equals bigger bills
2. Even though the rads are only lukewarm to the touch, we aren't used
to *any* form of heating on at night and it's making it difficult to
sleep
3. The pipes and rads creak and groan a lot which is making it almost
impossible to sleep!

Any advice?