PeteFJ wrote:
I had my Worcester combi boiler serviced last week, and the engineer
suggested that the system needed flushing out as the water in the system
was discoloured.

I spoke to a local plumber who told me that it if was working, then
leave it alone. He added that his policy was to leave well alone.
I might add that the boiler is working well.

So, as a consumer and householder with no technical knowledge what
should I do?

Thank you,
pfj

Fit a magna clean or similar then you can seen how much crap is being
collected. Flushing/adding cleaning solutions is to be avoided if
possible as it can expose/create other problems with leaks etc.

If you are getting poor performance then that is a different matter and
should be investigated.