Originally Posted by
KARFA
If going landside at T5 on arrival you would go through immigration and could use the arrivals lounge.
You cannot go back airside in T5 unless you have a bp for a T5 departing flight so the only option would be head to T2 using the landside options (HEX or tube). Once at T2 it will just be security to get in the airside departures area, there is no outbound passport control to go through.
I mistyped, i meant clearing immigration in T5 and going LANDside to use an arrivals lounge. Corrected in the above post.