Vanya, Danny, Pete
Thank you all for your advice - further investigation revealed that the problem lay with the hand brake lever itself, this had become very loose on the mounting plate, in particular the 10mm bolt holding the ratchet plate this was very loose and very deformed. I've replaced this and now things are very much improved. The main pivot for the brake lever on to the mounting plate is still loose and ideally I'd like to totally disassemble to firmly reattach (I imagine this needs welding back into place) - however accessing the mounting plate seems to involve removing the outer sill body panel? Something I'm reluctant to do due to the likelihood of damaging the paint. There may be a way of accessing from inside the car? perhaps cutting a large enough hole in the inner sill. Again any advice from those who have encountered this problem before gladly received.
Cheers John.