Gatwick Express branding is everywhere — but Southern trains to the same station cost half as much and take 35–40 min instead of 30. At Victoria the Express uses platforms 13/14 and Southern 15–19: tap in at the wrong gateline with the wrong ticket and you're charged the premium fare.
The rail station is at the South Terminal only. Land at North and you'll follow "Trains" signs straight into confusion if you miss the free inter-terminal shuttle (every few minutes, 2 min ride).
After the last trains (~00:30), Uber quotes jump to £120–160 for a trip that's £70–80 by day. Desperate arrivals pay it every night.
Gatwick is outside the London zones but inside the contactless area — a normal tap works fine. Tourists queue for paper tickets (often pricier, and railcard discounts don't apply at the machine default).