Currently I have: 1/2" LDPE incomer (as previously and helpfully
identified by this group). I get 20lpm at the kitchen tap. Between the
kitchen tap and the incomer I've got a traditional stopcock, 7 elbows
and 1 tee, and a water meter (responsible for all 7 elbows...) all in 15mm.

I've got three aims:

a) Reduce noise transmission to upstairs when the dishwasher starts filling
b) Get rid of the water hammer on the cold system.
c) Get flow rate higher if possible. I don't care about the flow at the
kitchen tap, just upstairs - hot water is via a megaflo, and the house
will eventually have two showers.

Is any of this *not* worth doing?

Change stopcock for a fullbore lever to improve flow. I presume I should
also add a draincock somewhere early in the system.

Redo the pipes around the water meter losing some elbows - possibly in
22mm, or 15mm with swept bends. It needs moving slightly anyway. I'm
presuming that a water meter doesn't depend on the structure of the
surrounding pipework - i.e. it's legal to mess around with it. I'm
guessing that it does need to be mounted vertically though...

Upgrade to 22m from kitchen to airing cupboard - already run via loft (I
realise I'll need to insulate it).

Ben