Thanks for the guide... BA's own website is useless and LHR's guide is not anywhere clear as well...

Just want to ask we are arriving LHR in BA28 (T5, 0455) and transiting to BA856 (T3, 1440). Would you advise us to go landside and use the T5 Arrival lounge instead of head straight to T3 and stuck at T3 departure lounge?

Also as we only have 2.5 hours transit time on our return leg from T3 to T5, any ways for us to explorer the T5 departure airside?

And we want to do some shopping in LHR, if we buy something in T3 departure airside, how's the pick up on return works? Thanks