We had a new piece machined from a solid piece of metal, threaded both sides of the spacer, with the spacer 2/3rds of the way along. We drilled out the old bolt, which gave us a hole in the driver's footwell, exactly as Craig said.
We tapped a thread through from the wheelarch into the footwell and screwed our new piece in until the spacer touched the wheelarch. We then fitted a nut inside the car and tightened it up. Finally we welded the spacer to the body.
Well done Ian, very neat looking repair--would seem that you have a 'pet' machinist as well as a 'pet' welder--a very handy combination when you're restoring old cars--look after them!!
Loading the car may be a bit excessive - the guys that did my alignment said it wasn't really necessary but if I liked I could put some weight in the car. As I have a pool at home, I loaded the little beast with 4x25kg bags of pool salt. It seems to drive well and the tyres still look fine as well so I guess the set up is OK.
The guy who owns the tyre/alignment distributorship is also a member of the local antique car club. I'm also a member and he poked fun at me for ages saying that he was a bit afraid of using the laser technology to align my wheels/suspension as one false move could have vapourised the car ... jolly joker