When I lived in the UK in the late 90’s I purchased new RHD cars from Belgium, Spain, Holland, & Germany.
There were normally two options in relation to paying VAT:
1\ If the retailer agree's, the vehicle is supplied ex-VAT with the VAT being paid in the country of export. You normally have to provide a copy of your passport and provide proof that you have paid the VAT – the garage requires this for customs & excise.
The main stumbling block to this is that the garages in the UK are not familar in exporting NEW cars. This is a recent phenomiman as the pound has got weaker. They may not think it worth the hassle.
If you are importing a car from the Benelux countries or Spain, the vehicle is typically exported ex-VAT as above.
2\ Pay the net price of the vehicle PLUS VAT. Once the vehicle is registered in the country of export and VAT has been paid, supply proof that VAT has been paid in the country of export and you can reclaim the VAT from the country the vehicle was purchased.
Again lack of familarity with NEW cars being exported from the UK, may delay the claim with UK customs & excise
If you import a car from Germany they normally use the above model re-imbursing the German VAT only when proof has been given that VAT has been paid in the country of export.
New cars that were being exported to the UK from Ireland in the late 90’s and early 00’s would have been exported ex-VAT. If you know somebody that works in the motor trade they might be able to give you some further advice.
Hope this helps.