Information about UK visas can be found on http://www.ukba.homeoffice.gov.uk/
If you need a visa letter, you can register to the conference (we suggest you choose "pay by bank transfer" because the "pay by credit card" is not yet available) and send us an email (info@wpw2019.org) to request the letter. If you choose "Pay by credit card" you can also request a visa letter, however, we would only state that you have registered to the conference. Once the credit card payment system is ready and payment is taken, we will then send you another letter that states you have registered and paid.