Yes, you can still fly.
If there is a no deal Brexit, that date, whenever that might be, will be limiting. Currently 23:00 on 12 April is next possibility.
What grips me is the total lack of EASA contingency on licensing. The UK have very clearly stated that they will grant third country validation for non-UK issued EASA licences to fly G Reg. EASA are refusing to do the same and ignoring the fact that Authorities have drowned under a mountain of applications. Well, at least those Authorities with a good reputation for processing routine work using days instead of months as a metric.
To make it worse the Authorities are not really following EASA guidance for mutual recognition of certificates. Primarily medicals being the choke point while the licensing teams wait for medical sign-off. Desk officers in the Authorities working their arse off, operators stressed and policy makers hiding behind the regulations and blaming the Authorities for not resourcing properly.
Rant over.