Just to quickly wrap up the LHR transport questions:
LUL Piccadilly Line will change its service pattern: Every alternate train will take the current T4-T123 loop, with the other trains operating T123-T5, thus no direct T4-T5 services.
Heathrow Express: Alternate Trains will go to T4 and T5.
Heathrow Connect: Will not serve T4 (no capacity). Might serve T5.
Jordan