Hi Simon,
It's cool to see you and your car are seeing the end of the tunnel! The car looks very nice in deed, it is a very neat built, and you can definitely be proud of yourself. And I'm pretty sure that once on the road, it is going to be an amazing car!
Don't try your engine too much, suspecting a head gasket failure, with the radiator on : I've ruined 2 radiators before I figured out the head gasket was dead on mine (I figured out that the compression from the cylinders was going into the cooling circuit, building up a pressure there that the radiator couldn't handle).
Good luck for the end, and keep us posted
