I too am having problems with their website for the last few days.

Trying to book some trips for March, April, May and June, I always book by Schedule, once I have my picked my outbound flights and selected my inbound flights, I keep getting a message that the seat availability has changed and to reselect my inbound flights and book by schedule, which I'm already doing.

Tried to change my inbound flights to the same destination. Also tried various UK departure points but always the same result.

Anybody else having the same problems. Also tried their mobile site today from my I-phone same results.

Best Regards
Flying Fireman