All
I keep statistics (sad maybe, I know), that I review in order to quantify probabilities.
In the last 9 months or so that I have kept stats, I have operated into LHR about 200 times for a large operator using shorthaul aircraft - ie fairly representative of an LHR user.
Now I'm not saying that I carry flight plan fuel by any means - far from it - but in those 200 rotations I have on only 8 occasions used more than trip + contingency fuel (15 mins), and on those occasions the most I have used above contingency was still only about 80% of my diversion fuel, in fact on only 2 occasions have I had to commit (the last time yesterday evening on a flight from a near European destination) as I usually plan to cover statistical holding at the 15% level from extra fuel.
LHR never fails however in it's capacity to catch you out, about 3 weeks ago, mid afternoon, 30 mins holding out of the blue in CAVOK esaterlies (18th Dec2002) and again yesterday evening - ok snow in am but lovely evening, but ground delays with no stands causing reduced flow rates inbound = 40 mins holding - very glad the ZFW was down 5 tonnes and I loaded 200 kg extra fuel!
Safe flying out there!