I'm sure I saw a lady on the desk the other week whom I'd not seen before - so she might be a newbie which could explain this.

Now this is an interesting one - something I have never tried but I have had a couple of colleagues tell me that they frequently use the GLA lounge on arrival if for example they want to do a couple hours' work before heading into the city centre for a meeting or whatever, and they say they have never had any trouble when I questioned it.

They are not on FT and not hugely experienced BA flyers (both silver but mainly just from domestics) so they would not really know that this is against the rules and be 'chancing it' - I think they just saw it upon disembarking, assumed they could use it, and seemingly succeeded!