from my experiences your little friends will be relatively comfortable....
they will be located in the 'bulk hold' which is at the back of the aircraft and it is not the same place as the baggage bins or cargo pallets.
unfortunately it is right at the tail of the aircraft and is therefore fairly steep but i'm certain that most loaders would ensure they weren't at the steepest part and therefore won't have their noses up against their cage door all the flight....
they are always adequately watered, but i'm not too sure whether they get fed prior to flight or not! as you appear to have a decent amount of flying to do i would of thought so, but feed them yourself before you go then anything else is a bonus for them... i've never known an animal to reject a second helping!!!!
oh yes and generally speaking the hold light will be 'OFF' so i hope they aren't scared of the dark!
the temperature will be set to keep the hold nice and warm so you have no worries there...
hope this helps
regrards
J6T