Getting an extension on my house which is costing e35,000. Builder says it will cost 450e for new flue kitt with existing boilder, and that as my existing gas boiler is 20 years old that it is better getting a new condensing gas boiler. He has recommended a Potterton boiler. He is charing 1,600 for boiler installation and boiler. Is this reasonable? Or is it a con? I think when some tradesmen see a woman on her own they think 'gullible'. I think he said the boiler was 100kw - maybe I'm wrong, but 100 something. The house with extension will only be 1100 sq feet. Thanks in advance.