A lot depends on where you want to end up in London.

Apart from the Gatwick Express there is also the normal Southern Train service to Victoria (and stations inbetween) which takes a maximum of 10 minutes longer or, if you want to be near the City of London or Kings Cross, there is the Thameslink service.

And they are just the direct services. For other places (Waterloo, Charing Cross for example) there aren't direct rail services, but you can change trains which is easier than having to haul your luggage into the Tube system.

Tell us where you want to go & we'll tell you how to get there, London is a big place and there isn't a single answer for everybody