If you choose The Sussex Bus, you can get five days travel to Brighton for £25.20. If you prefer Metrobus, a one week Metrorider will cost you £25 from the driver, or £23 if you buy one on-line, using their smartcard.
And, no - the two companies don't accept each other's tickets.
A weekly...
And there's also Service 270, run by Metrobus, for folk who like to think that their bus service isn't a B&H bus, even though it's owned by the same Go-Ahead Group.
https://www.metrobus.co.uk/download/11438.7/route-270-timetable-010912/?disposition=inline
Fares are here:-...
Service 40 - operated by The Sussex Bus, especially for all those folk who don't appreciate B&H Buses having a "monopoly".
http://www.thesussexbus.com/pdfs/service-40.pdf?v=5
And the fares are here:-
http://www.thesussexbus.com/pdfs/fares-40.pdf?v=5