So sorry to hear all you poor souls hanging around LHR because of the bad weather and delayed flights.
To me the infra-structure at LHR has always been stretched to the limit even during a normal operational period and a meltdown is expected during a snowy period . A relative new T5 can only provide comfort to the preveleged fews in the BA lounges but would have no effect on flight movements.
Since BA is unable to change the situation. May be they should have a Plan B of hiring temporary Thai masseurs (M & F) during the bad weather period and offer in-lounge massages (body or foot) to pacify their frustrated premium passengers!
Wishing you all getting home rapidly and safely!