Hi there - Se23 lurker here, bearing good news on the gate front.
I emailed Southern as I had serious concerns regarding Health and safety (having witnessed a man collapse on the steps of the footbridge and receive medical attention while a busy train load tried to squeeze past him). They've just replied stating:-
"I can confirm that the gate in the Perry Vale exit off platform 2 will now be left open whilst the station is open. After having reviewed this matter and now consider this to be the best option. As such this gate will no longer be closed after 2000.
We apologise for any inconvenience caused while this decision was being made."