That's great to hear. I knew it would be the cylinder :-)
So looks like I'll be replacing mine too. The Range Ultracal looks like it does the job. The Range brochure says I'll only need an 80l cylinder for my 2 bedroom house, though I think I might overspec it to be on the safe side and go...
I've been suffering from similar symptoms to Vince101 (boiler cycles when driving HW only) and would like to hear if replacing the HW cylinder fixes Vince101's problems.
I don't believe the story of the pump being too slow, given that the CH-only scenario works fine. The "resistance" of the...