(T) Doblo Spring Assisters / rear suspension?

I have a pre 2010 Fiat Doblo converted into a campervan. It was also a wheelchair conversion before it was converted into a campervan. The bump stops activate pretty often when you go over any reasonable bump and I wanted to try and raise it up or put some sort of suspension assistance in.

Has anyone had success with Grayston assisters or got advice on any other possible solution?

Check to see if there are heavy duty springs available.
Its pointless trying to assist something that is overstretched already.
My (later) Doblo WAV has heavy duty springs on and rides high. I also have to have commercial tyres fitted as the car is capable of heavy loads (although it won't carry anywhere near its capacity in my ownership).
The wheelchair conversion adds a lot of weight to the standard car with strengthening the back end to compensate for the metal cut out for the lowered floor. The camper van additions will have added a lot more weight so the standard springs (and tyres!) may just not be up to the job.
A quick Google shows a change of spring between mpv and Cargo, so a look in your handbook will show which has the greater capacity.

The 2010 - on Doblo springs are different rates for the 5 seat, 7 seat and Cargo.
The Cargo has a higher weight limit than either of the passenger cars, so it may well be the same for the pre 2010 cars.
As a comparison, my 7 seat has 300kgs less capacity than the Cargo version.

Thanks. Ok so my handbook says I should be about 1230kg. I then had the van weighed today and it came in at around 1530. So a fair bit over its rating.

Midland Road Springs do a heavy duty version for my model. They’re about the same price for Spring Assisters so is the consensus that some new double leave springs will be better than the Assisters?

New springs a much better option. The original ones will be tired anyway.
Assisters only start working under high compression so hopefully the HD springs will regain your proper ride height.