I have what appears to be a single pipe system? with microbore manifold downstairs, and I'm assuming another upstairs under floorboards, both with 3 radiators. The photo shows the downstairs manifold, and looking at the way the other radiators are connected, is there any reason why connecting another radiator to the 2 spare connections won't work?
Is the valve underneath for balancing or a drain?
Is the valve underneath for balancing or a drain?