Even worse when you add the £6-10k or so to prepare the boat and sail or truck it back to the UK (if you truck it you pay VAT on the shipping as well!). If you look closely the asking prices of ex charter boats ex VAT in £s is not a lot less than a similar UK boat, although in recent months prices have risen in the UK.
The only way it makes sense for a UK resident is if the intention is to use the boat outside the UK, either in the EU using the 18 month renewable rule described above or sailing off into the sunset. The number of people able to do this practically is tiny.