I'd imagine FTPE is fairly similar to FGW.
FGW training takes a minimum of 42 weeks, assuming the requisite 250 hrs, including 50 (or is it 40 - whatever) night is reached before the final assessment week.
For the course starting Feb 4th we were given week 12, 21 - 27 April, as leave, followed by weeks 24 & 25, 14 - 27 July, in the summer. The first lot of leave is pretty much fixed*, the two in the summer we're told can be fairly flexible. The summer leave takes place during front-end turns. Our DM at Oxford and the instructor at Reading have said that as long as we de-conflict any holiday from a couple of mandated classroom weeks (28 & 27) in August and another in October - then we are free to take summer leave when wanted.
It may of course vary for different TOCs and depots, but I wouldn't book anything prior to having sight of the course timetable, which you should see on day one. We were sent a copy prior to this but it varied from the one we are now working to.
*It can, and has for one chap, be shifted and swapped with one of the cab ride weeks, but it creates a bit of paperwork and is not something they seem to wish to see become the norm.