DG,
Noticed that you still have a cylinder. Over 20 years ago, we considered moving the cylinder and water tanks into the loft to give more space in the bathroom. The cylinder (& heating) was from a conventional cast iron boiler. Instead we opted for one of the first generation "combi" boilers mounted on the kitchen wall, which seemed to solve a lot of problems. Fourteen years later the boiler needed to be replaced with a second generation "combi" (condensing type). This latest boiler was installed in 2009 by a contractor whereas the first was DIY (which is no longer allowed). The new boiler is also serviced regular.
I was thinking the other night, has this been a cost effective upgrade, the original cast iron boiler, which supplied the cylinder and central heating would probably still be working, albeit in an inefficient manner regarding fuel usage, but I have been faced with two boiler changes, so any savings in gas must be set against every 12 to 15 years having to upgrade the boiler and pay servicing costs. It would appear when the decision is made to upgrade, there is no going back.
Nowadays I do the same as DM – 'get a man in' and just sign the cheque.