Hi fruitbat,

Absolutely agree with conmankiller here: get some more quotes.

Also - and apologies if this seems really obvious - but have you bled all the radiators (with the central heating system off)?

I have a similar problem with my house at the moment and I've had to make sure each radiator has had the air removed and the valve on each is open. Central heating is basically a network of pipes with hot water running through them, so the pipes at the start can get more hot water than others further along the network - opening and closing the small valve taps (if you have them) 'balances' the system so each radiator gets a decent amount of hot water.

I'm no expert on this - it may well be a bigger issue with the boiler - but it's worth exploring all the options (without damaging anything!) before you pay out mega-bucks...