I would hazard a guess Ed is talking about .. an unladen weight below 3,050kg are allowed to drive as fast as an ordinary car above 3,050kg the speed limits are restricted as vans / light goods vehicles ?
It’ll be registered as an MPV, the conversion company is registered as a manufacturer so would register it as such instead of the panel van that it arrives as. Actual weight of these is around 2,000kg - the plated max is 3,200 but they’re nowhere near that unless you fill them with bags of cement.
What weight limits are these Ed?