Sorry you'll have to wait for the UK site to come up, but the good news is that they are working on a solution.
According to the 2016 European Drug Report http://www.emcdda.europa.eu/edr2016 there are about 20mm regular users. That is roughly double the US count.
I figured it was a merchant account issue and having a U.K. store will solve the ridiculous fees they charge to run overseas transactions. In the meantime, they're negotiating wholesale distribution in Europe, particularly 400 B&M's in the Netherlands.
Beside a U.K. presence, you will likely be able to buy one from one of those retailer in the near future.
So they are going to have an online store for UK soon. That's good news, they are going to have an international presence. Did you reply to the email asking when they might have that site up and running?