OK, this is probably not DIY, but bear with me..

My aging Baxi Bermuda system is on its last legs, and I want/need to replace
it with a combi system so that I can reclaim the storage & header tank
space.

The existing radiator circuit is reasonably sound, although the majority of
rads are at least 20 years old.

Question: is there any mileage in getting someone to install a new boiler
(planned in the kitchen), picking up feeds to the existing system? The Baxi
is in the lounge, and as it is a converted bungalow, the pipework is fairly
"organic".

Otherwise, should I strip out the existing myself (and risk missing
something obvious), and go for a clean new install, or should I allow the
installers to do that, possibly reusing any appropriate pipe runs to save
work?

I think I know the answer, but I'd like to know from anyone else who has had
similar a dilemma.

Cheers,
Bramblestick