After spending 18 years working in ATC at NCL/EGNT, plus flying as a PPL, I can say its purely wind direction with 25 being into the predominant wind! Except at this time of year with a High pressure over the UK bringing easterlies hence the time recently spent on 07!
Plus the 25 take off is slightly effected by Callerton hill but it only really effected older heavy departures, Airtours transatlantic 767's would take up 8kt tailwind on 07 rather than depart 25! But that's a long time ago!! Most airlines still I believe publish an emergency engine out turn on runway 25??