"Danny" wrote
| I currently leave my central heating system on - constantly (during
| winter). When I'm out of the house I turn the room thermostat down to
| 20 degrees, when I return I pop it back up to 22-23 degrees, at night
| I put the system back down to 20 degrees. ...
| This question may seem silly but if my central heating system is
| switched off all day the house temp drops to approx 15-16 degrees,
| this takes quite some time to get to 22-23 degrees and I guess alot of
| gas also!

You could get a programmable thermostat, which will do this automatically
for you, so you could drop the 'out' temp down to about 17deg and have it
start warming up to 'in' temp before you return (assuming you have a fairly
regular lifestyle).

Your temperatures seem a little high; unless you have a need for such
temperatures (eg elderly or ill person in the house) you could try dropping
your 'in' temp a few degrees - my flat is usually 16-17C with the heating
on.

Owain