The gearbox mount was in a bad way, the original rubber having long perished and with a lump of rubber that someone had wedged in there to aid support. On top of that it was very oily underneath the car in general.
I started by cleaning the oil and grime off the sump, gearbox, etc and then removing the crossmember and mount after supporting the gearbox from underneath.
After cleaning everthing up it was ready for assembly.
To get the mount to fit into the crossmember, it is necessary to squeeze it using a vice or similar - first one end and then the other. I had a bit of a job getting the holes to line up exactly, but got there in the end. The mount is not symetrical so care must be taken to fit it the right way round.
It was now a simple case of finishing the assembly and putting the whole thing back.
Another little job was to replace the front/rear brake regulator torsion bar linkage bushes (I say replace, but there wasn't anything left of them!).
It was very easy to remove the linkage, clean it all up and replace with new bushes. At least I won't have that rattling noise any more.