@Trunkie This is frustrating because to me there seems to be no reason why you can't just stick a suitable beam in there without columns. Possibly because the resultant brick pier on the outside corner might not be sufficient to take the load? Or possibly the work take you within 100mm of the party wall and he wants to spare you needing an award?
I've counted bricks to guessimate the width of the offshoot as 3m, so with a new opening width @ 2.6 it might be one of these things.
Phone him up and ask why the beam can't sit directly on the masonry, and ask if it's one of the above, he'll probably not like being questioned, but it's his own fault for not giving better advice.
DW about BC - you can always re-submit the SE calcs before/after the work is done. Only a small job.