I'm looking for a large radiator (650x300x30mm+) that has small diameter hose connections - does the oracle that is this site have any suggestions? It's for a chargecooler system, rather than main engine rad. I was considering bike ones but they seem to be hyper expensive and large bikes tend to have two smaller ones instead, which is a faff, though offers some benefits.

You are describing a GSXR1000 radiator in size, it also has 28mm fittings.

They're concave though (not planar), so you need some depth to fit them in.

GSXR tattoos are not required though (despite what experts may say) if you go this route. I have a couple of them (radiators as well a tattoos!) if that's of any help. I am (unfortunately) in the land of the Undead (Cornwall) so I guess way out of your hunting ground.

Live long and prosper

Hmmm on fleabay the 1000 rads seem to be very tall/square (no dimensions given)?