You may end up not actually flying on a BA plane, as BA has cancelled a lot of its own flights in the past month(s) and moved people onto QR flights.

When you say "literally walked across the corridor" do you mean you skipped the security check in DOH? Yes you might get to skip it again, and the whole airport is more or less one terminal, so it is just a matter of finding the next gate, which might be nearby or a bit further away. Even if you have to go through security in DOH, it should be quick and being in Business class you get to jump to the front of the queue.

As you are in Business class you can use Al Mourjan.