you should do if you are flying first class on the inbound. Be sure to keep your boarding pass to show to the people at the entrance. They have 2 first class lounges in T5 - the concorde - reserved exclusively for those flying first class on BA - and the regular first class, mainly for O/W emerald. I think you will be able to use the latter, which is a very nice lounge. Definitely go for the Bollinger Grande Annee if you like champagne
