I just got this camper van:

https://www.quirkycampers.com/uk/for-sale/unleash-your-adventurous-spirit-with-our-custom-built-fully-off-grid-campervan-a-unique-wooden-haven/

It's a converted Citroen Relay II 1800 TD HDI MWB 2.8L with a tag axle, originally a mobile office for the police. It's 3.5t on the log book but the former owners said it's more like 4.3t fully loaded with travel gear. It's just passed its MOT with 2 advisories, including "Suspension bellows damaged but not to excess Rear and centre axle suspension airbags cracking (5.3.5 (b) (i))" The last MOT also said "Rear Suspension bellows damaged but not to excess 2nd and 3rd axle o/s and n/s deteriorated (5.3.5 (b) (i))". It's only done 23,000 miles, but half of that was in the last year, after a service in May 2022.

1. It takes over 7 minutes for the air suspension to build enough pressure to release the handbrake after being parked overnight. Is this normal? If not, could it be due to the problems noted in the MOT? Roughly how much would it cost to fix that?

2. When starting from a standstill, especially on a hill, or changing down a gear as the incline increases, there is a smell like burning plastic. The oil is fine, so I assume this is a clutch issue - though the clutch doesn't slip or show other signs of wear. What exactly is the problem, and how can I fix it? Is it likely to cause further damage if I drive it like this?

3. The van 'lurches' a lot when removing my foot from the accelerator (forwards), or beginning to accelerate (backwards), as if the connection between the body and engine is loose in some way. I don't know what causes this. I'm also not certain that it's worse than normal for a van like this - I've only ever driven small cars.

4. The recommended tyre pressure for the original vehicle is 60psi. Should this be increased due to the additional weight? How do I figure out what it should be?

5. Where can I get a proper evaluation of the vehicle? The garage that did the MOT said a full service only includes things like oil change and filters, and if I wanted them to look at other things like the clutch or suspension I'd have to pay them specifically for that. That's expensive (£90 each just for diagnostics), and there may be other issues that a qualified mechanic would spot that I haven't. The RAC do inspections, but not for vehicles over 3.5t https://www.rac.co.uk/buying-a-car/vehicle-inspections/compare-inspection-packages

Thanks!