A combi is unsuitable because you have more than one hot water outlet so thats why you need a heat only boiler and a cylinder.
Nothing to do with the number of rads.
That Vokera should be totally repairable. Having said that they can be rather difficult to identify intermittent faults on.
Tony
Thanks for that. We are a bit reluctant to get rid of the boiler, but have to say when it starts to act up in the winter months thats when it gets really frustrating. It always seems to be the same problem as I mentioned above. Having said that, we really don't know what boiler to replace it with anyway as there as so many to choose from and I suspect they all have their pros and cons.

