Gatwick South Terminal sees its heaviest traffic on weekday mornings and early evenings, when the M23 and M25 are shared between commuters and airport travellers. If your journey falls in one of those windows, building in some extra time is sensible; outside them, and at weekends, the roads are typically quieter. Either way, the route is planned around the traffic on the day, not around a fixed schedule that ignores it.
Your pickup point is confirmed ahead of time, removing any guesswork on the day, and flight tracking on airport journeys means the car adjusts to when you actually land rather than when the schedule says you should. The usual airport steps still apply either side of your drive — check-in and security, or passport control and baggage reclaim — and the included waiting time is there to cover them.
A quick note on group size and luggage at booking saves any surprise on the day: a saloon is comfortable for four with two large cases, and an estate, MPV or 8-seater takes the extra bags, buggies or kit that a bigger trip brings. Since school holidays and summer tend to be busier for journeys like this, booking a little ahead makes securing the right vehicle straightforward.