Sorry to mess with your head, but there are a couple of other options that are probably worth at least a cursory examination.
Estate Car Or MPV
It sounds like the 4x4 is your concren, not the trailer. A decent estate (M-reg Audi 80?) or a small MPV (Zafira?) might be the solution:
- Bit more economical
- More use through the rest of the week
- Likely to be able to make better progress when towing
- You're not 'losing' more money by selling the trailer as well
You might be losing some towing capacity, but is that really an issue - are you using all of it at the moment?
An MPV with a couple of seats out might give you more stowage space. Even if you have less (say with the estate), a bit of planning and bolting things to the trailer might solve that.
So I'd say it's worth at least asking the right questions and checking prices.
A Van (with the car stowed inside)
You have three options:-

.5t (Transit, LDV, Mercedes, etc.), van body or perhaps Luton body, or >3.5t (Mercedes, Iveco Daily). Choose a high roof model, so you can use the space as an office, kitchen, workshop and bedroom. The two key questions are:
- How many seats do you need?
- Will your car fit easily through the rear doors?
If the answers are good, then I think this is well worth considering. You are likely to be able to travel faster than with a truck, and might find more other uses for a van. With a bit of planning, and a couple of hundred quid's worth of 3/4" ply, you could create a very interesting multi-purpose conversion. Considering a van body, I would suggest:
- Install 'running boards' full-length, over the wheelarches, on which the car will sit.
- Install a solid floor
- Under the running boards, you have stowage space. Use some for custom-built cabinets (which also provide the vertical support), others are 'holes' to place your toolkit, gas stove, etc.
- You now have a large space under the car. Plan how all your other kit will fit in there.
- Your ramps can sit on the top of this gap when in transit. Design in a drip tray (or locations for one) so the items beneath are protected.
- Make the section of the running board by the side loading door removable.
- You could buy a permanent side awning unit. Or, with some tarpaulin, a sewing machine, and some custom-made poles make one that is water and wind proof, and perfectly suited to your needs.
- Plan everything to be dual use. It should serve one purpose in transit, and another when you are in the Paddock. When you arrive in the Paddock, it should take 15 minutes to unload and set it up as your Paddock Unit.
- A roll of carpet along the running boards, and you have a bench seat. Another along the floor, and you have a decent base for your bed. For transit, you roll them up and stow them away. Alternatively, flip the running boards so you have seat on one side, friction surface on the other?
- Two stowage boxes come out and stack to create the stand for your stove?
- Then remember to make everything bolted down for security in transit, and removable (so you can use it as an ordinary van)