I think Britannia and Air2000 are part of the same company - (might be wrong here).
Sorry, but thats wrong, Britannia belongs to Thomson holidays, which belongs to an even bigger company in Europe. Air 2000 are part of Cosmos holidays.
I'm sure when we flew in Europe with Britannia it turned out to be an Air2000 flight.
This is possible under code share agrements and charter arrangments. If one travel company isn't going to fill an aircraft, then this tour operator will sell its seats on the aircraft to other tour operators, or something like that.
As far as the original topic is concerned, Air 2000 are OK, as far as a charter airline goes, they are better than some I guess. I find all UK charter airlines to be very simular - Britainnia, Air 2000, jmc and Airtours, however Airtours' A330 is a very modern nice plane, it has seat back TVs and computer games, and the toliets are downstairs creating a more pleasant aircraft, they utilise this aircraft on most Orlando flights.
Charter airlines have very small seats, the food is well, typical airline food (interpret that how you like), and the IFES are usually main screen only. Drinks are not usually free, although a drink with a meal might be provided.
Ratcat has the best idea, fly with Virgin. Thier prices are good, they have good equipment, I think they use the Boeing 747-400 on Florida routes. Each seat has its own PTV, the seats are bigger as it is a schedualed flight, not charter and the food and service is fab and its free drinks throughout the flgiht. One advantage of flying with Virgin, or BA for that matter is that they both fly to Orlando International (MCO) which is closer to WDW and Orlando attraction areas, rather than Orlando Sanford (SFB) which is about an hour or so away, which the chaters fly to.