Scanscan,
I think you will find all JAA operators have to have at least "final reserve" fuel remaining at touchdown. This is 30 minutes (holding mind, not G/A's etc which would eat it up much faster) endurance. I have never been close and hope I never do. This applies to destination and alternate. If at any time it appears that you might land with final reserve only you MUST declare a full mayday, so in the hold at LHR this would need to be at around 40-45 minutes remaining to allow an approach to be flown. Like I said, hope it never happens to me.