Moderator, Iberia Airlines, Airport Lounges, and Ambassador, British Airways Executive Club
Join Date: Feb 2010
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Posts: 63,791
Yes indeed Clareym, welcome to Flyertalk and welcome to the BA Forum. Please continue to post here, it's always good to see new people in this forum.
The general rule for shorthaul outside LHR and LGW is that bag drop will open about 2 hours, or sometimes only 90 minutes before departure, and I think that's going to be your working assumption. In Manage My Booking in the flight details it may give more information (but not always).
I have to say I found it unfortunate that at MRS you didn't manage to get to the lounge. It's en route to the gate, it's not the largest airport, and if checking the bag 2 hours beforehand I'd normally expect to get at least an hour in the lounge. I guess there was a long queue in security, but if flying CE there is a fast track on the left hand side (takes you into a corridor) which should have assisted you.