I've not tried this completely myself, but i've taken it all the way through to the final payment stage and it seems to work!
TerminalA.co.uk is offering £6 Quidco cash back per booking at the moment....
If you search ryanair.com and find the flights you want, then go to terminalA and search for them using their lowfare search option, you will find them for £0.01, Terminal A then add their discount of £1.02, making the flight cost -£1.01! Lol.
If you go through the booking process, you HAVE to pay £3 for airport check-in and a £4 service fee, making the total £6.05 .
At the payment stage, it definatly says ' Total to pay £6.05'. And you can pay with any type of card.
So, providing Quidco tracks, you will get the flights for 5p each :-) .
(Make sure you book return flights as 2x one way flights in separate transactions to get 2x quidco cash back! Same applies to the skyeurope budget airline cash back, book as two separate one-way flights for the same price as the whole return and get 2x£4 cash back via the sky europe quidco link!)