Kevin B is correct, if you pre book excess luggage its cheaper but you have to book it 4 days before you fly. I didn't know I was over till the day before flying, which is when I phoned them to see if I could pre book. I was told my booking was closed, had been closed for 4 days and that I had to pay the excess at the airport. I pointed out I didn't know I was over my limit till I had packed and that i didnt ever pack 4 days before I had too!! Was told its £10 per kilos, I said that was very high, that other airlines charged £7 or £8, I was told "oh you may pay that at the airport, £10 is only an estimate!!!" Then charged the £12