change in your favor...................price adjustments for a currency are easy to do. I'm sure he accepts payments in almost any currency.....PayPal/your bank do the conversion anyway. If a model cost $100 in 'pounds', then the price in Euros will be reflective of the rate between Pound and Euros....( this AM it's 1.36 EURO PER POUND...SO 136 EURO FOR A 100 pound model )...no matter what you pay with, he'll be just fine. Same process for USD.
You PAY in your own 'native' currency, your BANK/PAYPAL do the exchange rate and he gets Pounds........what's the difference? Running the store thru an English site may have some other legal benefit to him or he'd not be taking the time to do so, or he may be under some regulatory/economic constraint to do so. ALSO....since he is selling in POUNDS, that means he is obligated to collect the VAT on these sales if they are made to an UK address, and he should be subtracting the VAT from sales OUTSIDE the UK....but, as I understand the system, crediting the VAT is NOT obligatory....so there's your reason to sell from UK, and extra 15-16% 'profit' on sales outside the UK for which he does not need to transfer a VAT tax collection to the Royal Treasury per such sale.
Strictly my opinion............
NOW, SELLING ONLY 80 MODELS IN THREE MONTHS, AND HAVING THE INVENTORY COUNT GO UP 60 IS NOT A SUSTAINABLE BUSINESS PLAN.....that means his 'net' sales are only 20 over the 3 month span....not too good, unless he gets a heck of a mark-up per model.