I am considering replacing my conventional boiler with a combi-boiler
and during the replacement I will probably also relocate it. One
option is to move it on the same wall but closer to the origin of the
pipework, i.e. I will only need to cut the existing pipework not
introduce any new joints except where they actually connect to the
boiler. The other option is to move it onto the opposite wall which
will involve new pipework.

I have done plumbing before and am reasonably confident but for
obvious reasons I am a little wary of messing around with Gas. The
controller is also fairly old and will need to be replaced. Also
there are no room thermostats although I have fitted thermostatic
valves to every radiator, so do I actually need one ?

If possible I would like to do most of the work myself and get a CORGI
man in to do the final connections into the boiler. Any ideas how
realistic this is ?
Can I re-use the existing pipework or will I have to run new pipes
throughout the house ? Do I still need a separate pump or will this
be built into the new boiler ? Should I consider doing this in two
phases, i.e Central Heating first and Domestic Hot Water second ?

I'd like to minimise the amount of time we are without hot
water/heating. Anybody aware of any web resources which may advise
the best approach (i.e. order of activities) ?