A bit more...

If 25lpm @ 2.0bar 25lpm @ 1.5bar might be a problem as you seem to
suggest (measured at top of house) would it help to replace the 15mm
from the stop cock at ground level with 22mm pipe?
I think the lead inside diameter is more than 15mm but less than
22mm. It's about 7m of vertical pipe to get to the boiler if I put it
on the top floor as I propose. (Rooms about 3.5m high on ground and
first floors).

(Doing my best to give you all the relevant info without writing a
book.)

Frank