I will have an overnight connection in LHR. I am comming in on BMI (term 1)one evening and departing mid day the next on BA (term 5). Ialso have reservations at the yotel in T4 for that evening.

My question is, when I arrive, should I transfer to T4 Airside and then clear customs in T4 or should I clear customs in T1 and then try to get to T4 landside?

Iirc, I can go T4 - T5 the next day via an extension of the Heathrow Express, right?