Hi Stephan,
Sounds like a good plan. We are all part of the EU so if you pay VAT in one country then it is valid for all I believe. An £11k boat is not likely to be brand new and so should have the VAT already paid unless owned by a VAT registered business. You would be prudent to get proof that VAT has been paid - e.g. copy of the original sales invoice if possible.
You could wait for RIBEX2005 if indeed there is one in 2005 or check out the ads here and on
www.boatsandoutboards.com . A second hand Ribcraft 585 in decent condition with a decent engine is likely to be £15K or so. You might get one with an old tech 2 stroke around the £11k mark but you would have to be fairly lucky!
Hope this helps,
Alan