As with most things, getting planning permission for 23L/05R required compromise. Part of this was agreement 106 with the local councils, which basically limited use of the new runway when traffic was below certain levels (had a quick google, but haven't tracked down the fine detail yet).
As traffic levels are now increasing, the airport seem to be aware of the fact, as they are currently conducting a trial extension to the opening hours Mon-Fri 0530-0930 and 1200-1900 GMT (I think that's 30 mins longer in the morning, and 2-3 hours longer in the afternoon. If holding at a weekend lunchtime is becoming prevalent I imagine that those hours will also see expansion ultimately.
I would guess that other than hardcore NIMBYs, now that runway 2 has been in use for over a decade, a gradual expansion of it's hours will be a lot less noticeable than it would have been from day 1.