If you’re from outside the European Economic Area or Switzerland you may need a visa for the UK, Standard Visitor visa . The Home Office recommends to apply up to 3 months before planned trip to the UK and it costs £85. For full list of countries that require visa, please follow this link .
For the visa application you will need an invitation letter – please email one of the members of the local organizing committee.
Visa information:
https://www.gov.uk/government/organisations/uk-visas-and-immigration
Visa fees: