Ryanair flies between: London - Dublin, London - Dublin, London - Dublin, Paris - Barcelona, Barcelona - Paris, Birmingham - Dublin, Birmingham - Alicante, Birmingham - Tenerife, Manchester - Dublin, London - Berlin, London - Malaga, Malaga - London, Madrid - London, Madrid - London, London - Madrid, London - Madrid, Bristol - Alicante, Malaga - Barcelona, Manchester - Alicante, London - Tenerife, as well as several other routes.
Ryanair has quite a famous reputation for their baggage policy. Make sure to meet their requirements as they are extremely strict with all weight and size policies. Note that you must pay for all checked baggage and the maximum weight cannot exceed just 33 pounds! Make sure to book your baggage online prior to departure as you will pay significantly more at the airport, sometimes up to $200! You are entitled to one carry-on item, but it absolutely cannot weigh more than 22 pounds and cannot be larger than 55 x 40 x 20 centimetres.