Just one additional point to add to those above, it was noted on entrance both to the CCR and Galleries First at T5 that my guest's flight was due to leave after mine and that she would not be permitted to remain in the lounge after I had left the lounge. The request was made very politely both times and I didn't even question it (my guest didn't want to stay longer in any event), but I'm not actually sure whether this requirement is specified in the applicable rules.