But that nightime alternation programme is pretty meaningless as it also states:-
"the runway to be used if weather conditions... ...preclude selection of the preferred runway".
I would reckon 90% of the time the surface wind would decide which landing direction to use - not some "political" choice.
I haven't been able to find any figures for wind speeds at LHR at night, but remember that the preferred runway is used unless it would have a tailwind of more than 5 knots. In other words, when an 09 runway is preferred at night, it will be used unless the wind is 5 knots or more westerly. Since (I believe) wind speeds over land are generally lower at night, I suspect that the "political" choice is used rather more than 10% of the time.