Not too difficult. Many companies have done this. You will need to incorporate and have a registered agent in the UK. Access to banking will be one of your biggest challenges (luckily, the UK application does not make it mandatory to have a UK bank account to file an application).There are many companies that pra service to out-of-UK enterprises to help them get licensed within UK. Neopay is one such company (no affiliation): Neopay | Be Confident In Your Compliance.