Thank you all for this, I had been trying to find some information on spring dimensions for ages with no success. It is the correct spring I believe and some of the dimensions seem to tally, no lowering block. However when I split the spring to clean it and there is a fair bit of wear on the leafs where they rub on the ends, also when I put the rear suspension back together there is a lot of slop in the bushes etc so I am going to bite the bullet and buy a new one whilst it is still a 10 minute job to change.
Back to my local supplier to complain about the new rear flexible brake pipes being too short and supplying the wrong bushes for the radius arms!