Thanks for the suggestion. I'm a bit cramped for room (pipes are boxed in), but if there is room to fit one I'd certainly rather do that than pay for a power flush.
I've had some very confusing behaviour out of my Worcester 24cdi. It seems to be functioning normally in terms of heating and hot water, but recently I tried to add a little pressure (it had dropped slowly over a long period) and the pressure didn't rise, even though I could hear the inflow of...