Flew CDG to LHR on Saturday with BA. Flights operate from 2B/D at the moment while 2A/C are refurbished.
British Airways checkin is in 2D but departures (security) is in 2B. I think the only lounge available to you is the Extime lounge. Once through security you descend a level and take the compulsory walk through the duty free shops which appear to be managed by Extime too. On leaving the shops look ahead of you for a Relay news shop and a La Dupree shop - between the two there’s a passageway to an elevator which will take you up two floors to the lounge.
The lounge was pretty decent, it was quiet when we arrived but busied up as it’s used by multiple airlines. It has all the usual facilities. It is before passport control soo you might want to give yourself time to reach the gate as there are no stairs down, only the elevator and this can get busy. Passport control was efficient but it might be busy at peak times. The BA flight left from gate 30 and ground staff did a good job of managing boarding. Sorry, can’t tell you anything about smoking facilities, if there are any available they weren’t prominently displayed.