Stripe, the red hot US startup that gives developers an easy way to handle online transactions, has begun issuing invitations to a limited beta service in the UK, as it starts to test the water in Europe ahead of a future expansion beyond North America.

Update: In what we’re putting down to a bout of Valentine’s Day confusion — or a desire to keep the launch quiet — Stripe co-founder Patrick Collison tells us that emails about the UK beta were sent out to some users “in error”. So, despite some employees confirming the UK launch, Collison claims it isn’t happening. We’re continuing to look into this.

The company, which enables websites to take payments simply by adding a line of code, hasn’t announced the UK beta, but numerous developers (see: here, here, here and here) have mentioned on Twitter that they have landed a much-sought-after invitation. Equally telling, a number of Stripe staff have referenced it too.

dsdsds 520x244 Web payment enabler Stripe begins testing European waters with UK beta (Update: Stripe says it isnt)

Founded by brothers Patrick and John Collison when they were on vacation in South America, Stripe expanded to Canada in September 2012 in what was the first international roll-out of what it said will be many.

“We’re already working on the next set of countries. Watch this space for updates,” an announcement at the time read, and the UK — alongside Germany and France — is an obvious next step for the company, which is valued at an estimated $500 million.

When Stripe does make the full-time move to Europe, it will come up against a rapidly growing rival, Paymill. The Rocket Internet-backed company raised $13 million in funding last month, which it has pledged to spend expanding into new markets and beefing up its 25-person team.

Paymill first launched in Germany back in August of last year but today it is live in 32 markets across Europe. That’s largely due to a massive expansion in November which saw it quietly launch in no fewer than 29 new countries over a weekend.

Last year was a busy one for Stripe and it raised its $18 million Series A round in February, before bringing in another $20 million when its Series B closed in July. Its backers include Sequoia Capital and Redpoint Ventures, and angel investors Peter Thiel, Chris Dixon and Box co-founder Aaron Levie.

Interested developers can sign up for notification of the UK beta, and other future developments, here.

Related: Stripe launches Checkout with overlay payment form and mobile support optimized for Android and iOS

Bonus: Startup Grind has an an excellent story on how Stripe was formed.

Image via Thinkstock