Ummm, if you cancel the DD with the club at the end of the second month you're charged 2 months DD plus £50. The £50 is, if you like, an early cancellation fee. I've never heard of anyone being charged for the whole season if they cancel reasonably early. If you pay in full at the start of...
Sorry, but I can't believe this is an accurate representation of the facts. If they are accurate, simply phone the club and you'll get the £50 back. Alternatively, perhaps have another go at explaining here what actually happened?
Are you sure they want the £50 on top of the two DD payments they've taken already? I'd have thought that since the season hasn't started and thus no games have been watched, they would refund the DD's taken less the £50 cancellation charge. No?