All new Oceans should be M1 PLG Body Type Motor Caravan
Even My GC 600 is M1
There are 3 parts to the registration:
1 M1 or N1 - all Californias should be M1 - a vehicle who's primary purpose is the carriage of people not goods. Builders van are registered as N1, camper vans converted from builders vans remain as N1
M1 or N1 normally makes no difference to the user - only recently have places like the Rotherhithe tunnel started to discriminate on that basis.
2. Body type - for Oceans / coast & Beach is motor caravan, with the exception of the beach tour which as it doesn't meet the criteria for a "motor Caravan" is registered as an MPV - ie the same as a car.
Body type is more important for van converters, this is what dictates uk speed limits MPV or Motor caravan = car speed limits, getting your log book changed from N1 panel van to N1 Motor Caravan is important for converters.
3. Tax rates - this for recent Calis only! Anything registered as a MPV is effectively a car & taxed as such ie £165 a year + the over £40k supplement.
Around 2018 / 2019 there was a change to the tax rules that meant motorhomes were suddenly liable the over £40k supplement.
When this supplement came in some of the major motorhome manufacturers got all upset & campaigned to get it abolished, it created an anomaly whereby you could buy a £39k van & have it converted after registration & it have cheap tax compared to one that was converted before registration, they achieved this towards the end of 2019 I think.
From then on all Calis benefitted, however rather than put them in the same rate as cars but without the supplement, they reverted back to PLG - Private OR Light Goods at £295 a year - this as the same category as for vans (Light Goods), foreign imports, and anything else that they don't always have the full emissions data for.