However with the engine in the car I just could not get the belt on to the rear of the pump. Problem was that I couldn't get the pump over the mounting studs with the belt on or if I put the pump on first could not get the belt over the pulley as not enough clearance.
I also took off the pulley cover plate from under the car and tried it by fitting the pulley to the pump pulley first then fitting it over the cam pulley second, but there is a lip on the cam pulley so that wouldn't work either.
Finally I found a solution. I removed the four studs from the mount and used bolts of the same length to mount the pump to the base. This completely eliminated the issue with the studs and made fitting the belt so easy I had the pump on and off a couple of times and the timing set and everything tightened, all within 10 minutes.
Here's a picture of the mount with studs removed showing replacement bolts
This shows the pump with a bolt holding it on whilst setting the timing.
Ian.