When stopped at platform 4 on Monday, only the rear 2 doors were off the platform (well, one was at a very narrow part and the other would have been just off the ramp). We are not sure how far along the platform the service went, as it extends, at a narrow part, across the bridge. We were stopped clear of platform 5 and the junction as a service left from platform 5 not long after our arrival.
As far as I am aware, they have UDS (Unit DeSelect) like the 185's. The plus point though being the corridor connections, of course.
I suspect it could be possible to lock out the doors on an individual basis and release from the local door control in the middle carriage. However, I'm not sure if such is standard practice and on a busy service (which, to be fair, is most of them!), there would be no way to get to the local doors to lock them out