If I was married the money would all have been pissed up a wall long ago; but I'm not, and the idea of free hot water for the rest of my days did appeal. So I went for the full package. The new system has a thermal store, which is huge, and complete integration with the existing boiler. It has only come on two or three times that I know of in the last couple of months.
There have been a few teething problems and I think there is more tuning to do. For a kick off the water temperature in the store is higher than that in the hot water tank. The latter is difficult to gauge and I am wondering if I need a thermometer installed on it.
The other problem is that the new system is dumping heat (into the heating circuits) at far too low temperatures. Presumably I should be able to raise this by tweaking the software.
It feels a bit odd just turning the hot water on, pouring it down the drain and not having to give a damn, but I'm sure I'll get used to it.