thanks dan
at one stage i was going to sell the van as i don't use it much but we decided to hang on to it as it's a good tow vehicle for our caravan ..
we put coil over shocks on it some years ago for towing so maybe they have given up will have a good look this week also going to check the bump stops just in case they are worn..
i have been looking on rockauto's site and they have air shocks at £42 a pair and a small compressor for £102
so i might go that way
Only problem you'll have with a built in compressor, is you have to carry it on board all the time and mount it permanently.
If you own one of those battery jumper / tyre inflators, or a portable tyre inflator, ( I use a tiny rechargeable "Airman" inflator the size of a coke can) just take it with you to pump up the shocks, you don't need an on board compressor, the air shocks from rock auto etc usually come with some thin tubing and a schrader valve.
If you mount the valve out of the way ( mine went next to the number plate light but it could go behind the bumper or anywhere easy to get to but out of sight) you can just put the caravan on and inflate the shocks via the valve until the car levels out. The shocks aren't like airbags, they should just stay up until you unhitch the van. ( mine are so effective I have to let them down a bit to unhitch). Then when you are hitched up again, just re inflate them.
It works for me, and it's now just part of my routine when I couple the car to the caravan.
They're so effective, i came home from York Drags a couple of weeks ago and because I'm so near, I didn't bother re- inflating. All the way home it drove like shit, until I stopped and put some air in and it was back to normal. Maximum difference for small outlay. Hope you find a solution that works for you. Cheers, Simon