Mulligan,
We checkin and get a flight plan with a 'minimum' company fuel requirement stipulated (to be legal). We (captain and first officer) look at this, the weather, traffic situation, NOTAMS, etc. and decide on a fuel figure - generally more than what the company flight plan says. We then phone it through to the refueller.
No dispatchers this end. It's the crew who decides. Only takes a few minutes (if that) to come up with a figure. Have never been contacted/pressured by the company to justify a decision.
In EU-OPS it's the captain's responsibility to load the appropriate fuel for the flight. This responsibility is delegated by the company to the captain and vested in law. End of the story in my humble opinion (as an FO)!
