Hiya, the costs in Brighton and Sussex can be really expensive if you don't go out of your way to save money. The campus Co-op is extortionate at best and Brighton can be a really expensive place to live. There are good ways to save money (trains into Brighton are cheap, shopping off-campus at Aldi, taking advantage of deals, offers, free stuff etc)
It's really up to what ease of living you want. I'm happier to pay more money for ease in most cases as I'm a lazy ******* and can afford to. I have friends that live really comfortably off not much money at all.
I hope you come to Sussex, it's a great time.
Good luck!