If there's no room for your buggy and you can't clearly take the twins out, then it seems you'll be waiting for the 2nd or 3rd bus and hope there is space for it in the area.

However passengers sitting in the fold up seat area of the P4, should move for a buggy or wheelchair.

On another note, a parent got on the 185 outside the Jenner with two children, one was about 3 and the other under 12 months which she carried with a Baby Bjorn. No buggy in sight and no real issue in transporting both children.