I found a local place which said they could rust treat the underside of my car, said they could do it all for around £450 so I took it round and discussed them doing a partial job, as my main concern was the rear arms and odd bits here and there that I really wanted doing - the rest was as new, treated at the factory. Whilst there could they replace the final sections of brake pipes front and rear. With absolutely not rush to do it and no urgency within limits to return it. They wanted do do it in warm weather, when the treatment works best.
They chose a time to take the car, when I had just been in hospital for surgery on my back and I was unable to drive, so I asked that collect the car and return it which they did a week ago. They are a couple of miles down the road.
I am only just able to take a look at the work and I am disgusted - they charged me £430. I had already been quoted £160-ish over the phone for a through end to end steam clean and then waxoyling, but that was the far side of Leeds and the more local company claimed there substance was much better than Waxoyl and what the 4x4 guys insist upon.
They only did the rear pipework, but all the way to the existing joints under the floor - fuel tank dropped down, to fit as original, though I did agree they needn't run the pipes as original. What I could see of it, looked fine.
However the rust prevention work was a complete waste of money, they cleared off any loose then just sprayed the black stuff on, made the surface of the underside at the rear look pretty, never even took the rear wheels off to do it, obvious from the overspray onto the backs of the wheels. covered the underside of the rear arms, absolutely none inside the easily accessible cavities of the arms and the top of the arms are untouched - this after stressing the arms were my main concern for rust. The black could be anything, it's just a matt black look to it.
I managed the photos, by copy, paste from My Images...
These are the upper sides of the rear arms, which I had asked them to pay special attention to with the rust treatment. None at all on them, but the easy undersides look pretty.