Kuchan
The vote is tomorrow which will determine what happens next.
As I understand it - if the UK exits the EU without a deal (& assuming the EU does not implement a reciprocal two year transition period), your UK CAA part 66 licence will only entitle you only to issue CRS on UK registered aircraft after 29th March. This will remain valid for 2 years during which you will have to apply for a 'new' UK licence.
In order to issue CRS on EASA member state registered aircraft after March 29th you will require to convert your current UK licence to another member state issued licence.
Hopefully either - the deal will be voted in or, if not the EU will implement the reciprocal transition period. Fingers crossed!