Hopefully it will be the long-awaited announcement that anyone who still has DPM kit (and can still fit in it) should go to their local TA centre to be issued an S*R, bomb up, and start gatecrashing house parties.
I can help you out with this one...
2300 mean 11 o'clock in the late evening (o'clock being short for "of the clock".
BST means British Summer Time, which is that part of the year when the clocks have been put forward by one hour. It isn't short for; "British some of the time" in this context.
I hope this helps.