[mehereathome]

Not recently, as Robc says Jet2 offer service to get a ball park figure phone or e-mail them, one of basic requirements is a suitable size, regulation travelling cage/box, major carries are likely to be dearer.
Procedure little different to checking a passenger in, just that the check in is normally at Cargo areas, in Lisbon animals are collected from oversize luggage area.
You need all correct paperwork, pet passport, out & return, the UK return side is stricter as there are only a few airports you can fly into, even with new regulations.

Pet Travel Scheme « Defra

Hi - I am moving to Portugal this year and have two dogs and a cat to take. Was going to drive the dogs and fly the cat - was being the operative word am now taking all of them in the car. I called Jet2 to get a price for the cat and almost fainted. I am going one way and cost was almost £600. They have to go in a AFTA approved carrier which you buy off them. So no idea what the return fare would be. This is the cost of flying into Faro, if you want to fly into Lisbon or another airport it becomes more expensive because there are less flights.