My 2 cents. Any boiler change, for a standard customer I charge at least £750 up to a £1000...Labour... for friends I've don't £500 for a few days work, but luckily i don't have many friends.. for close family £150 or something so they don't cost me money... I charge half what British gas would, so i don't loose sleep at night over my prices. They get a years no fuss guarantee on my work and obviously anything that comes with the appliance installed.
I like when this subject comes up, always interesting to hear how people charge... especially the guys that tend to be up north doing new boiler installs for a few hundred quid