If not deal found (what I ll really find it surprising ... But this Brexit thing seems to be more about politics playing for themselves than really consideration for the people living in the country ...)
So ... If no deal found. I believe like said before, me I have an EASA licence but I m flying in Uk for a UK airline. So I believe Uk CAA will give me a UK licence based on my EASA so I ll have 2 licence. Now when I ll go to the sim to renewed my rating, it will only renewed my UK one, and I ll have on my own money to do the same test with private ATO to renew my EASA rating if I still want to be apply to apply to any EASA country.
But again I will be surprised if UK CAA doesn t stay with the European open SKY.