all the above makes very interesting reading and both brings some clarity and confusion at the same time.
To summarise:-
the SSL kit provides a significant change/improvement on plus 4 and 4/4 models of various vintages (£750)
On plus 8 models the improvement is less clear cut (mine is a plus 8)
The AVO shocks make a change/improvement on all models which may not be as significant as the SSL kit (£350 front and rear)
With the AVO kit 'shortening the rebound springs' should help. (this I don't yet understand)
In all cases chrome kingpins are recommended, which probably includes bushes and reaming (which adds about £300 to the job and something I hadn't accounted for). This on its own my be responsible for much of the harshness of my suspension.
I like to do all the work myself, that way I understand whats happening and can QA the job so there would be no labour charges but I'd need to get the bushes reamed or buy a reamer.
Have I missed anything?
Now I need to find out about 'shortening the rebound springs' which surely cant be a drastic as cutting a bit off with a grinder????
thanks for all the comments so far
Gary