I am about to have a very old central heating boiler replaced. My plumber is saying he would recommend fitting a standard Potterton boiler, as he has good experience that these are reliable, compared to a Vallant which he said were not so good. Or are they much about the same in terms of reliability etc. Or does anyone else have any other recommendataions please ? Thanks. PS I have natural gas and have ruled out a combi because of the large size of the house.