Just thought I'd give a little update on this issue.
Haven't solved this 100% yet but today I had my cousin in the car who is more mechanically minded than me (to be a fair a pieve of cardboard is more mechanically minded than me)
Anyway I started the car up and he commented on how much it 'rocks' and suggested the engine mounts were knackered!
I was playing round with the car by putting it in first driving forward a little then jabbing the brakes and each time it knocked, then it also did it when I cam to a stop and pulled off, excuse me if this sounds dumb but I thought this could be the engine swaying if the mounts are knackered?

Anyways I'll have it checked out and post back
