A Kaffenback frame seems fine value at £128 but I'd rather pay more for nicer tubing (725?) – what options are there for say less than £400?

What do you want to use it for?

Oh well a touring bike so steel with mudguard and pannier mounts. Would use as a winter bike for road rides.

Yeah, good for that and good VFM. Just asked in case it was for cross.
The old Pompino has done well over the years from urban posing to touring to the 3Peaks. I think the Kafenback is pretty much the same bike?

I have both the Kaff and pompino

Ignor the lables 725 etc the Kaff rides so well it is almost comical especially compared to my Shitespeed opps I mean litespeed

I had a Argos custom Audax bike which I sold because the Kaff is a nicer riding bike

Dunno where you live but I am in Devon if you want to try one