EdV

Hey, need a little help on upcoming itinerary:

10/2 AA108 BOS-LHR arrives 0650. BA766 LHR-OSL dept 1245
I would assume this will be a T3 --> T5 transfer (based on flight schedules and posts here) right? Being Plat, AC member on Y ticket what would be my best use of this time? Just head straight to T5 and the Terrace lounge? I won't be able to access the AC in T3 correct? Also, is the routing really as simple as off AA metal, transfer bus to T5 and through security there?

10/7 BA763 OSL-LHR arrives 1315. AA155 LHR-BOS dept 1805
Guessing this will basically be a reverse of the above? Again, what would be best use of my time? Would I only be able to access the AC in T3 here? Or could I access the BA arrivals lounge and is it worth it?

Thanks in advance!