FOlks

Quick boiler question...

I currently have a Saunier Duval combi boiler installed in my house.
The install dates from 1987, i.e. before I lived there. It has been
running fine, although possibly not terribly efficiently of late (my
perception).

At a recent routine service, the engineer (the same company as I've
used for some years) says that the boiler will need some fairly major
parts replacing: heat exchanger, pump etc, which will cost a few
hundred quid. I was expecting this. He then looks at the pipework
leading in and out of the boiler, and tells me that it is actually the
wrong size (15 mil instead of a larger size- maybe 22mil?) and points
to the various step-down pipe adaptors fitted there to enable just
that fact. I actually knew about this already, since another engineer
from the same company had told me the same thing some years ago, so I
am not too surprised to hear it again.

My question is this. Is the wrong size pipework a major problem;
should I have the current boiler repaired or should I have it
replaced, and in the latter case, would I have to have a condensing
boiler fitted rather than another combi? I believe there are new
regulations about boiler efficiency coming into force next Spring?

One more thing. Bear in mind I will probably move house next year.

tia
Dave P