Cheers for the links.
I already use a triple set up ... water separator, pressure reg &
oiler, and had that connected to my portable compressor (10Lit) tank
using RECTUS type 25 connectors - in fact I use these connectors on all
my air tools as the internal bore is so much larger than standard
schrader fittings. Found that frame nailer & dry wall stapler would
frequently jam on standard fittings (BeA rep advised change to RECTUS)
.... the sudden spurt of volume needed immediately after the drive
action to retract the piston fully)

I want to keep to single phase and 24 Lit receiver for portability, as
this has proved useful in the past ...

I also have a separate 50 litre receiver which I can plug into the
compressor to give me larger volume should I need high volume of air at
any time- but to be honest so far have never found a need for it.

Considering an 8 bar 7 cfm model ... a Clarke Ranger 35 (1.5Hp)
which is reduced to £60 +vat to get a 10bar ver the price hikes to
£130 + vat and up to £150 +vat to get higher cfm of 8.7 (2Hp)