Heat only boilers are also known as conventional, traditional, open vent or regular boilers. If you have an old heating system with a hot water cylinder and water tanks in the loft, it is likely you have a heat-only boiler, and you can replace like for like.

You would not have to change pipework and remove the tanks and cylinder, so it should cost less. Remember, though, that you should always have a power flush carried out to clean the system so that you are not fitting a new boiler onto pipework filled with sludge.