Why would the radar room have to be on the airfield site? It could be anywhere, just needs good data links. I know it won't happen but interesting to discuss. Think of London City. Not a single controller on site! As for the radar at Don, I believe its still there.The radar room at LBA could probably squeeze in one more position to service another airfield's approach radar function but the room itself really couldn't be enlarged. A few years ago, Thinking Space pulled off a spectacular TARDIS job on the room but a facility with more floor space would have to be elsewhere on the airfield site. Hopefully this is all academic anyway and I'd be amazed if LBA would even consider providing ATC services to a competing airport.
Anyways, what became of the actual radar head at Doncaster? Is it still there or did Peel redeploy it?