I am doing a minor TP run next Wednesday: LGW to GLA b2b, then four hours later LGW to AMS b2b. The question I have is, upon my return from GLA will I have to exit via immigration then go back through again for the AMS flight out of LGW or can I just go to the lounge(as Silver) on arrival from GLA and then go straight to the gate for the AMS flight in the afternoon?