Lil wrote:

Assuming we clear customs quickly, what is the fastest and most
convenient way to get to Gatwick and somehow manage to grab some
lunch? Is there a shuttle between airports? Will we have to cab it?
Whatever ideas come to mind, please do not forget to include
approximate cost for the transport.

There's a regular shuttle between the two airports - it takes a bit over an
hour, and costs GBP15. Check www.nationalexpress.com for information on
times, etc.