Below is some heavily recommended prospects to consider - majority of them have potential that is Football League Championship or even Premier League.
The Football League Championship potential is basically top flight potential in any other nation in the world, so do not overlook them. None of the prospects are FM17 wonderkids. None of the prospects will fit right in your first team. All these prospects are either on Non Contract, Amateur Contract, or Youth Contracts, making them low risk gambles in the event of an hard Brexit.
Any La Liga 1 mid table club or any La Liga 2 clubs work well in scouting cheap talent
Go looking in any top 3 flights for cheap talent. Some of them are more interested in flipping youth talent than developing them.
Real Sporte Clube have best facilities in the third tier. Do not overlook smaller second tier clubs.
Do not overlook smaller clubs in Serie B and Serie C. Most have put their emphasis in their youth development.