Found this article in a magazine that clarifies the maximum speeds you can legally travel on different types of roads in the UK. It all depends on whether your log book states motorhome or van and the max and unladen weights of your motorhome.
a collection of top tips, tricks and ideas, DIY improvements and motorhome modifications that can also be made to caravans, campervans and RVs. Many of these modifications I have made and used on our own motorhome but I have also listed other tips, advice and product reviews that I have found on the Internet including ideas for day trips and visits.
Motorhome Mods UK 