There are various improvements you could make to your heating system without the need to renew your boiler. Old timers and thermostats can be replaced and thermostatic radiator valves added to make your heating system more controllable throughout the house.
If your existing boiler is in need of replacement, you could choose from a new, highly efficient condensing boiler, or a biomass boiler, running on wood chip. Alternatively you could consider a renewable/ microgeneration energy source, such as a heat pump.