Problem sorted. It wasn't the spring so I had a look at the tracking next. It was quite a way out as the body of the car is not the original and to get it tracked I removed 9 shims. This appears to have sorted the camber as well.
I've noticed that the camber of my rear wheels are not the same and the drivers side sags a bit. I have taken the spring out and replaced it but this has not fixed the problem. Any ideas!