Found this:
Info on UK speed limits for vans, also covering pickups, dual-purpose vehicles and car-derived vans - on Parkers Vans and Pickups
www.parkers.co.uk
What are the speed limits for campervans?
There are only two manufacturer-built campervans sold in the UK: the VW California and the Mercedes V-Class Marco Polo. Both are legally allowed to drive as fast as a regular car.
Campervan speed limits - VW California
However, the two brands have gone about this in different ways. The California is classed as a 'motor caravan', while the Marco Polo is labelled an 'MPV'.
Where you do need to be wary is with third-party campervan conversions based on regular vans. Check that the V5C registration document has been changed to 'motor caravan', otherwise you'll be subject to the same speed restrictions as the van it's based on.
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