Thanks for the info John.

I will have to look up what is necessary to change the HW from gravity
to fully pumped.

I read that it is not a good idea to have too many thermostatically
controlled radiator valve as it cuts down the efficiency but we only
have them in bedrooms.

As for the original balanced flue it exits the house at chest level.
With a wall hung condensing boiler the exit for the flue will be at
about 7 ft. I didn't know if there were any building regs for the
condensing boiler flue like with conventional flues. I seem to
remember my father having to build an insulated stack up to the roof
in the past.

I expected to add a cylinder stat. and upgrade my room stat. and
chnage the programmer so I guess I am a little better prepared now.

Now to find a corgi fitter who doesn't charge the earth.