The new Koni shockers were fitted front & rear yesterday. The difference was apparent immediately. Now the Patrol feels as though the suspension is firmly attached to the chassis instead of bouncing at each bump. The missus is really impressed. Had the Firestone airbags fitted too just to allow the rear suspension to cope when the van is attached. Dale did a wheel alignment and found the front near side to be 4mm out. So now it tracks true. Its just like a new car.
Thanks Appollofish and others for your advice.