I am not too sure if someone has mentioned it on this thread, but Customs & Excise explicitly require lounge operators to admit only passengers that are LEAVING from the same terminal. So it seems as if your only choice would be the T 1 lounge (and the arrivals lounge in T 4 of course). But however law-abiding you may be, T 4 departures lounge may still be worth a try - if it is worth it is another matter though... ;-)