A friend sent me details of this Ryanair offer. It's not advertised on their website, you have to put in the dates you want and see if the price comes up as £00.01 per flight. I've just booked for the 4 of us to go to Klagenfurt, Austria as dp has family there. I paid £105 total, which is just taxes.
Fly for free, just pay the taxes, on 10 routes from London
Book midnight tonight to midnight Monday 3rd March
Travel between 14th March and 15th May except over the
Easter period, 14 days advance purchase required
Seats available 1200 hrs Monday to 1300 hrs Thursday
and Saturday after 1200 hrs
London Stansted to
Brussels Charleroi
Stockholm Vasteras
City of Derry
Newquay
Stockholm Skavsta
Strasbourg
Nimes
Klagenfurt
Malmo
Shannon