Fantastic - thank you for the advice. I thought it was odd that nobody had mentioned it before and I thought that other waste would dilute it. Many, many thanks!
I'm getting new heating system - new radiators (are those old fashioned 3 column ones any good?), shower in the bath and new boiler in a two bedroom flat and, usually, just me living in it. I've been led to believe a combi condensing boiler will be the best and I can get rid of the rubbishly ineffic...