Replacement meter cabinet?

[Sharpend]

So I have a customer with a park home which has a recessed cabinet which would like to change for a surface cabinet but would prefer a much smaller cabinet than the standard size cabinets.
Can I just use an IP rated GRP cabinet/enclosure or does it have to be a specific type of cabinet/enclosure? The meter is purely for private use as electricity is billed to park owner and individually billed to each unit via their own meter?

Was thinking of something like
https://www.expertelectrical.co.uk/hellerman-grp-enclosure-nsyplm-ip66

 

[kerching]

Park homes are a strange beast. You may have to have discussions with the site owner as they think they have first dibs on everything. I can't see an issue with a smaller enclosure

 

[Sharpend]

At the moment it has a combined large analogue meter with rcd and main switch all in the one enclosure which is fixed inside the meter cabinet.
The rcd is 30mA which conflicts with the CU inside the unit. So was thinking of replacing the main switch for an rcd 100mA TD and a smaller digital meter. Haven’t got regs book to hand for reference as to whether the first rcd is a requirement if the cu has sufficient rcd protection?
If digital version may be more accessible