Handbrake Mechanism sticking on?. Had exact same problem with my 2a, Especially when moving and you put the clutch down it knocked quite a bit. Try slackening the handbrake off with the 7mm adjuster on the back of the handbrake drum. Or could be Buggered engine/gearbox mounts, Or like said, UJ's are nackered.
S1 With a Transit DI engine, Bet that ****er flies!
Let me know how you get on.