Just a note on London travel zone tickets: if you’re only here for a day, they’re rarely worth it and substantially more expensive than using pay as you go.
Each zone has a daily cap if you use either an Oyster card, or your bank card with contactless. Sutton and Barnet for example are both zone 5. Assuming you don’t go any further out (and you wouldn’t need to), the absolute maximum you’d pay, peak or off peak, is £12 for unlimited journeys in a day. In reality, it’d be less than that if you’re getting the tube, overground or bus to the ground and then to somewhere in central London for a few drinks (usually about £6).