Captain Sensible
Having been subject to Cirrus flight plans in BA longhaul for some time now I have to say that I use the fuel fig as a guide to minimum acceptable and then add suitable amounts to that.
For instance, on shorter flights the 5% contingency figure can be way below 1000kg and if arriving at LHR at say 0615 you will need at least 20 mins holding - 2000kg or more. Add a bit of typical early mist and drizzle and I would not consider anything less than 5000-6000kg over and above Cirrus. The cost of diverting just for a "fuel & go" far outweighs the marginal extra cost of the fuel, the majority of which remains on board to used on the next sector......