I would recommend OLCIing them in, PYOBPing, and if they don't have email/printer access - select the "FAX BP" option, to get the BPs faxed to where they are staying.

I would suggest they arrive one hour before departure. It is VERY hot airside, and the fry-up at Burger King doesn't help. They can pay for access to the Sunjet Lounge if they want. If so, tell them to turn right immediately after security, past the luggage shop, and up in the lift (opposite Burger King) to the first floor.

The BA flight goes from pen number 4. It is a pen, and resembles something you might herd sheep into, and is a particularly unpleasant place to stand, waiting for the bus to the plane. Newpapers are in the pen on the right.

LCA is good at priority boarding, so if they need extra time boarding, do tell them not to be shy but to make themselves known when they annouce pre-boarding, which means they will be on the first bus, will be first out of the pen, and will avoid the worst of the mad dash to the steps up to the plane.