Just because this page is entitled Summer Schools doesn't mean visitors can't come to Mayo in the Autumn, Winter or Spring! In fact, as far as prices go, that is a great idea and as for the weather . . . much the same as summer but a little colder.
Contact the people concerned, tell them when you want to arrive and see if they can run a school/course for you and your friends.
Without exception all locations are in breathtaking places, where, after lessons, it is possible relax and enjoy the superb nature of County Mayo or have great fun in pubs in the evening.