We had three known good mounts, and one known bad one. So Barry removed the bad one, and roughed it into place using my steering rack subframe.
Barry: This did mean the shell had to float in mid-air to gain access. Be assured it wasn't as dodgy as it looked, as the rear was still on the jig on one corner, and the whole shell was being supported by the crane in the centre.
Still, rather you than me!