Non UK Vat Paid boat visiting UK

[Saintgeorge]

Does anyone have any experience or guidance on bringing a UK registered boat, exported at original point of sale to EU so non UK vat paid, being sailed back to UK? My understanding is UK VAT is payable on its current value..is it liable immediately or is there any temporary permission to visit or transit through? Also, who decides what the present value is? Many thanks in advance for any help with this