Richard, as an oveseas visitor, you are entitled to use the VAT retail export scheme. The link to the full regs is here:
http://customs.hmrc.gov.uk/channelsPorta...tyType=document

An extract is here:
The VAT Retail Export Scheme allows:
certain customers to receive a refund of VAT paid on goods exported to destinations outside the European Community (EC) subject to conditions detailed at paragraph 2.3; and
retailers to zero-rate goods sold to entitled customers when they have the necessary evidence of export and have refunded the VAT to the customer.
This is a voluntary scheme and retailers do not have to operate it.
The following text has the force of law
Retailers and refund companies (see paragraph 5.5) may only operate the VAT Retail Export Scheme when they comply with the conditions set out in this notice. Briefly these are:
the customer must be entitled to use the scheme (see paragraph 2.4);
the goods must be eligible to be purchased under the scheme (see paragraph 2.6);
the customer must make the purchase in person and complete the form at the retailer’s premises in full (see paragraph 3.1 and 7.4.2);
the goods must be exported from the EC by the last day of the third month following that in which the goods were purchased;
the customer must send the retailer or the refund company evidence of export stamped by Customs on an official version of Form VAT 407, an approved version of Form VAT 407 or an officially approved invoice (see Section 4); and
the retailer or the refund company must not zero-rate the supply until the VAT has been refunded to the customer (see paragraph 5.2).

So find a dealer willing to apply the scheme and save 20%. I suspect Uncle Melvyn may be your man.

Thank you all guys. Feel more normal now!
Ken in Sweden

Thanks Dave - Uncle Melvyn is the man - he has the paperwork too

Although daveW is right in principle, dont go thinking you will get 20% off the retail price, the V.A.T calculation is not as simple as a straight 20% off. it has to be worked forward from the net price.

16.66% off VAT inclusive value.

I live in New Zealand and occasionally trip over to the UK. I have bought Morgan parts VAT free and had then shipped to me in NZ (had to pay GST and duty in NZ).
I have also collected parts from a dealer in the UK (the one that I bought my Mog off) which I took back with me to NZ. I paid the price, minus the VAT, for these items after the dealer checked with their accountant that I could.
I have also been down the Form 407 route, but not for Mog parts.

All goods that enter the Uk from outside the EU must have the 20% duty paid before you can receive your goods through customs.

I have operated vat export scheme for our customers from outside the eu, in a nutshell, they pay full price at the till, I fill the form detailing goods and vat content - currently 1/6 of total price, they show the goods and get the form stamped at port of exit, they post the form back to me and I then credit the vat to their visa card etc less a handling charge.