So - thanks to Pete's red cross parcel and some more pipe and fittings from ebay, the radiator is now finally complete and plumbed in:
I used a 45deg copper elbow to match the angle of the outlet on the bottom of the rad and a 90deg copper to get the coolant flowing up to the stat. After assembly they where given a coat of engine enamel. The connection from the thermostat to the top of the copper piping is a standard BMW hose that has had the end chopped off:
At the other end, there's a CBS 180 degree rubber hose to bring the water back on itself:
To keep it from flapping around, the pipe is attached to the bottom of the radiator - there are two oblong eyes on the radiator to which the pipe is cable tied to (Ah - cable ties. Is there no end to their uses?

). I've used a couple of lengths of rubber mat to keep the radiator from rubbing on the pipe.
At the other end of the engine, the heater feed pipes have been installed. They make their way through the bulkhead via a couple 3/4" double ended spigots.
Here they are on the other side:
I also managed to strip, repaint and test the mini heater box. No leaks, so that was good! I followed Pete's example for the front bracketry, and made the rear ones with a couple of rivnuts apiece
I also knocked up a small bracket to hold the heater valve.
The valve will be held on with a couple of cable ties (Again!) once the pipes have been installed:
So - a weekend of piping and brackets!
Oh - and POR15 & Engine enamel...
They'll all go back on once they're dry. Here's hoping that the next update I'll at least have a date for the big bits from Marlin!