RoosterBooster,
I did the full time course at Lon Met too so can't advise on the distance learning brush-up weeks. However, if you're in full time work and you really don't want to take 3 weeks off, I'd try and manage it so the weeks that you go in for cover subjects like Gen/Radio Nav, Instruments, A/C Gen etc that you may have many questions about. Subjects like Law, Comms, Ops can easily be studied at home. So I guess if things are tricky regarding time off from work, then missing these lectures would cause the least damage.
Regards,
B