Gatwick Airport to Stansted Airport

There may well be buses, but train is probably faster: you can look up times and book at http://www.nationalrail.co.uk/

Santiago to Madrid takes most of the day; only recommended if connections in London are poor (or you want to visit Madrid of course )

National Express http://www.nationalexpress.com/ normal daily timetable from Gatwick to Stansted. The standard price is £25.

Departs Arrives Duration Changes Details Facilities

02:10 05:00 2hrs 50min 0 View WC
04:05 07:00 2hrs 55min 0 WC
05:30 08:30 3hrs 0 View WC
05:55 08:35 2hrs 40min 0 View WC
06:20 09:05 2hrs 45min 0 View WC
07:10 10:25 3hrs 15min 0 View WC
07:55 10:35 2hrs 40min 0 View WC
08:05 11:05 3hrs 0 View WC
09:20 12:20 3hrs 0 View WC
09:55 12:35 2hrs 40min 0 View WC
10:20 13:05 2hrs 45min 0 View WC
11:20 14:20 3hrs 0 View WC
11:55 14:35 2hrs 40min 0 View WC
12:20 15:05 2hrs 45min 0 View WC
13:20 16:20 3hrs 0 View WC
13:55 16:35 2hrs 40min 0 View WC
14:20 17:05 2hrs 45min 0 View WC
15:20 18:20 3hrs 0 View WC
15:55 18:35 2hrs 40min 0 View WC
16:20 19:05 2hrs 45min 0 View WC
17:20 20:20 3hrs 0 View WC
17:55 20:35 2hrs 40min 0 View WC
18:30 21:10 2hrs 40min 0 View WC
19:20 22:20 3hrs 0 View WC
20:20 23:00 2hrs 40min 0 View WC
21:45 00:25 2hrs 40min 0 View WC

There are youth hostels http://www.yha.org.uk and other cheapo backpackers' hostels in London itself - depends if that's your scene. Don't think there are any around STN or LGW though. Plenty of other accommodation; expect to pay GBP30 for B&B or guest house, more for hotels. Either book in advance or at the airport when you arrive.