And finally....

Ideally want to replace street to house with 32mm blue as suggested
previously by folks here so...

I've trenched out for a new water main to the opposite side of the house
and can chop into the old black pipe right next to the water meter
(under the boundary wall) as advised by the helpful water board man but
connections are proving to be challenging.

I've micrometered up the old pipe and it has an outside diameter of 21.5
to 22mm (3/4") which I want to plumb in a length of 32mm and convert
back to 25mm in the house by going through a 32mm to 25mm and on to the
22mm copper tail to which I've added a full-bore 22mm lever valve.

Where the pipe enters through the upper level foundations (800mm below
ground level) and comes into the utility/boiler room about 8" above the
worktop (lower level of the house) I was thinking of either a 32mm
stop-cock into 25mm or simply skipping the poly stop-cock on pipe entry
into the house and going via a few 90 degree bends to the floor then
onto the 22mm copper/lever valve.

Main concern is getting the old black poly to 32mm in a single joint and
whether it would be foolish to skip the poly stop-cock on entry point to
just rely on the 22mm copper 1/4 turn lever valve thing where I'll feed
into the house cold feed?

Cheers
Pete