I have read plenty of articles over the past year about Brexit and the Fintech scene. The truth is none of us really know what will happen, particularly around our abilities to passport to the European markets. One thing does appear to be happening already though, it is proving harder to attract the best tech talent from Europe. A good piece in the FT on this recently: https://www.ft.com/content/7e7d4462-375f-11e8-8b98-2f31af407cc8.
It will be an interesting 12 months whichever camp you are in