The Commission have made it clear that the referendum result changes nothing about eligibility for these funds. UK businesses and universities should continue to bid for competitive EU funds while we remain a member of the EU and we will work with the Commission to ensure payment when funds are awarded. The Treasury will underwrite the payment of such awards, even when specific projects continue beyond the UK’s departure from the EU. The UK will continue to be a world leader in international research and innovation collaboration, and we expect to ensure that close collaboration between the UK and the EU in science continues. Details can be found at:

Statement of the British Treasury 
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/545767/CST_letter_to_SoS_for_DExEU_August_2016.PDF

Statement of the British ministry for universities and science about H2020 projects
https://www.gov.uk/government/news/statement-on-higher-education-and-research-following-the-eu-referendum

Statement of the European Commission about H2020 and Brexit
https://ec.europa.eu/programmes/horizon2020/en/news/outcome-referendum-united-kingdom