Although outside of the Club's area, I noted on Saturday that the National Trust is running a promotion next week (Tuesday 26th - Sunday 31st August) allowing free travel to Devil's Dyke and Ditchling Beacon (B&H services 77 and 79 respectively).
The offer is only valid on the mobile app, and entitles the user to one 24-hour citySAVER ticket. Various other terms and conditions apply (and the NT don't seem able to make up their mind whether they mean customer, member, or user), but it may be of interest for a day out, especially to anyone using the train or car to reach Brighton, and doesn't qualify for free travel in other ways.
Chris