Unfortunately, yourself and many others are in what appears to be an uncertain position re VAT. If you have the original bill of sale, including VAT details, then you are _probably_ fine. Assuming you do not have:
You will require proof that your vessel was constructed in the UK prior to 1985.
AND
You will require proof that your vessel was physically present in EU waters on 31st December 1992.
If you cannot provide BOTH of these items, then you are potentially without valid VAT exemption documentation, and are therefore potentially liable to pay the VAT.
As I write, the RYA are in communication with HMRC, and are putting together a new F.A.Q. about the whole VAT situation. This is due to be published on the RYA website some time around the beginning of February 2008. They do not say they are negotiating for change however, so I anticipate that it may simply be a re-iteration of the facts.
The RYA have a member's questionnaire online which they have been using to collect details of any incidents occurring involving boat owners being queried on their VAT status. From what I can gather, the results of this seem to be that very very few people have had a problem. In fact, reading around the net, it seems that a great number of people are travelling around the EU in vessels of questionable status without problem; so it may well be that if you are the relaxed type, you do not need to fret about the situation.
Arguably, your biggest problem will come when you decide in the future to sell your boat on. If your potential buyer is aware of the VAT situation, they may well require that you prove the exempt status to them prior to completing the sale, or reduce the sale price by the appropriate amount (17.5%).
I suggest that you take the following actions:
1. If you are not already a member, join the RYA. They have a wealth of information on their website which is extremely readable and to the point. As a member you also have access to free advice on various email addresses and telephone numbers they publish online for members only. RYA website is here:
http://www.rya.org.uk
2. Attempt to dig out the appropriate documents for proof of VAT exempt status.
2.1. Original UK bill of sale including VAT details. Contact the Virgo owners club - perhaps they know a way of accessing original sales invoices.
2.2. Builder's certfificate. Again, get in touch with the owners club and see what they can tell you.
2.3. Proof of location on 31/12/1992. Once again, it might be that your boat was in the ownership of a member of the owners club in 1992 (unsure if the club was running then). If so, they may also know where the vessel was kept at the time, and _they_ may still have records.
(I think the moral of the story here is that you should join the owners club if you have not done so already)
Best of luck with getting sorted out. I guess this is a heads up for the future for yourself and other readers to do some through research before buying ANY boat, and don't take the word of the seller - regardless of how well meaning and honest they think they are being. Many people are not fully aware of the VAT situation.
If any other readers have anything to add to the above, please do!