Greetings to everyone at Flyertalk, this is my first post.

I wish to connect at LHR to a Paris-bound flight. I realize it would be easier if my bags were ticketed through, but for various reasons (I’m flying on unrelated airlines) I have to be prepared for the possibility that I’ll be obliged to go landside, pick up my bags, clear customs and immigration, and slog my way through to check-in at the appropriate terminal.

From reading other posts, it seems that transfer buses between terminals at LHR are only available if one stays airside. And once having gone landside to pick up my bags, I can’t get airside again until I get my boarding pass. I can’t get the boarding pass, it seems, until I check in at the appropriate terminal at LHR, in which case the issue of access to the transfer bus will be moot.

My flight from Canada is scheduled to arrive at LHR term 3 at 7:00. I’ve got a choice of connecting to a British Airways flight, departing from terminal 4 at 10:15, or an Air France flight, departing from Terminal 2 at either 10:15 or 11:15.

If I allow an hour to pick up bags and clear customs, 0.5 hours in line at the check-in desk (I’m assuming that time of day will be busy) and another hour to clear security, reach the gate, and make the boarding call, I’ll already have used up 2.5 hours.

Question: can I physically slog from terminal 3 to terminal 2 in 0.5 hour? How about terminal 4? (I generally travel pretty light.)

Thanks in advance for such help as anyone can give.