Don't just look at the old potty as a gas guzzler. Many older heat-onlys go on for 30 years, with very few repairs and sometimes little sevicing. You have to cost in the short life, parts and labour needed of modern boilers as well.
Fair point, but the saving on my current EDF tariff is in excess of £800 p.a. My Hometeam contract costs £204 p.a. and covers servicing and all parts. And even the Potty used to need servicing - about £70 p.a. For me, the combi has been brilliant, but I've got a protected boiler room with a drain so no freezing up problems at all. But my neighbour has had her new combi freeze up a number of times and is tearing her hair out whenever it gets frosty!