I'm friends with a couple CS professors at a Russel Group university, and they said that since last year the number of EU students applying for funded PhD positions went from hundreds to nearly zero this year - and several students who were going to start studying this year have pulled their applications, quoting brexit concerns. At our company we are trying to recruit for about 10-12 programming positions, and we had two programmers from EU who were deep into the recruitment process and they both resigned citing that they don't want to commit to living in the UK because of brexit.

The process is not even fully defined yet, and it's already scaring people away - but things like less PhD students won't be damaging until 3-4 years from now, and then everyone will blame whatever else but brexit. Things might not be going down the drain right now, but there's no way it will turn into anything positive for years.