Although you suggest this is only the 3W, unless I am corrected the rules apply for everything.....where there might be a difference is if an individual is purchasing direct from the factory on UK plates, then taking it to another Country, he will of coarse be rewarded with a piece of paper that proves he has paid his dues.
If the vehicle is less than 6 months old VAT must be paid in the country to which it is imported. If it has been registered on UK plates VAT would have been paid in the UK and a refund may be applied for. Special temporary plates are available for vehicles which will be exported from the UK, VAT is not paid but must still be paid in the country the vehicle is taken to. If the vehicle is over 6 months old and less than 20 or 25 years old some countries, particularly the Scandinavian countries still charge high taxes before the vehicle can be registered.
There have been some dodgy systems in use to try and avoid VAT payment on vehicles imported on temporary plates but the authorities are pretty much awake to this now and also watch out for any false invoicing.