Is there any limit as to how early you can arrive at MAN T3 if you are connecting rather than coming from landside?

I've got a longish connection coming up (incoming longhaul into T2 on QR, connecting to a BA flight to LHR from T3) with about 5hrs in between. Have read mixed reports on how far in advance of flight time you can enter security from landside (3hrs seems to be common?) but can't seem to find anything about flight connections.

Actually entertaining myself in T3 for that length of time is a separate challenge of course :-) albeit with lounge access I doubt it will be a particular hardship.