I've been at BA for a few months now and I flew before I joined them. I don't think they are a social bunch of people down route. The flight crew normally meet down stairs in the hotel bar for drinks but from my experience I've never been invited to join them. Maybe I've just been unlucky to be night stopping with selfish crew. At my previous airline night stops were rare and when you did get one even with minimum rest you certainly made the most of it. Flight crew and cabin crew alike. I take it you'll be a member of the flight crew joining so you'll be fine. Just don't expect to see any cabin crew in the bar because they will be in their rooms watching their free movies, that's LHR EF crew.