Now I have finally installed it and it works well.With a standard pivoting arm the TV can be easily lifted out and then hangs at a lower height than the locker in which its housed,allowing for easy viewing.
TV reception is an issue in remote spots.I have a simple signal booster which helps, although I need 240v hook up for that to work.For a while I despaired of finding a signal but then it clicked that I had to retune the TV when away from home,as the local transmitters have a different wavelengths.
The option that will give signal in the remotest of spots would be a satellite dish.This is pretty big to store in the van, especially the size needed to get signal in Scotland(or an even bigger one needed to get UK signal in northern Europe).Professionally made campervans often have a retractable dish on the roof but there are also portable collapsible options. I have decided for now to stick to a very simple aerial, and the smallest of all options ,a 15cm stick aerial with a magnetic base to temporarily attach anywhere on the roof or walls of the van, outside.(actually it also works with in good reception areas inside the van.This has given me acceptable signal in the Lake District and in North Yorkshire, and the Peak district.I may give a conventional aerial on a pole a try,but again this would mean more paraphernalia to transport in the van.