The UK will become an Associated Country to Horizon Europe. UK researchers can already access funding under Horizon Europe on equivalent terms as organisations in EU countries. While the final steps to complete UK association are pending, Imperial researchers can, have been, and are encouraged to continue to apply to open Horizon Europe calls and opportunities. The UK Government has now announced that successful applicants for Horizon Europe grant awards will be guaranteed funding if delays to association impact access to funding.

The European Commission's main page for Horizon Europe: 

https://ec.europa.eu/info/research-and-innovation/funding/funding-opportunities/funding-programmes-and-open-calls/horizon-europe_en

The European Commision's FAQs on UK participation in Horizon Europe:

https://ec.europa.eu/info/sites/default/files/research_and_innovation/strategy_on_research_and_innovation/documents/ec_rtd_uk-participation-in-horizon-europe.pdf

The UK Research Office in Brussels Factsheet on UK Participation in EU Programmes for Research, Innovation and Higher Education:

https://www.ukro.ac.uk/Documents/UK_EU_factsheet.pdf

UK Government funding guarantee in the event of delays to UK association to Horizon Europe: 

http://www.gov.uk/government/news/uk-government-provides-financial-safety-net-for-horizon-europe-applicants