FlpasOne,
I`d be interested in your AIC.
At our company we typically depart for LHR with trip fuel, altn fuel (EGSS mostly), final reserve(30 min), and a statistical amount of contingency fuel, which has a minimum of 5 min.
Now, this contingency fuel will in some cases be more than 20 min (as it is statistical), but more often it is closer to 10 min.
Regards.