Gatwick to Heathrow
 

My flight lands at LGW at 9am on Sat Dec. 20th....British Air is sold out of the LGW to EDI that day (they have a 7pm flight).... but BA has a flight out of Heathrow at 1pm.......my questions are......what is best way to get from LGW to Heathrow ?? and would i have time for the 1pm flight ???

Do a search. There are numerous threads on this subject.

Just to get you going:

www.gobycoach.com

You may want to check out the train that takes you from Gatwick to Victoria Station and then the train to Heathrow. There should be some information on the Gatwick Airport Website or go to www.baa.com that is British Airways site. You can take a bus (70 minutes)or take the Gatwick express and then the Heathrow Express. Both are trains but I can't speak for how long all of that would take versus taking the bus.

The 2 express train combos would have to involve the underground or taxi as the Gatwick Xpress comes into Victoria stationand the Heathrow express leaves from Paddington station. Point is, it's not the best, quickest, easiest way with all the trabsfers, especially if you are draging kuggage with you. And I don't even want to talk about cost as each train is around 12BP and taxi/tube would be another 5 or so, with the final cost of 30BP per person(that's about $50US now).
The bus is about 11 or 12BP per and a great deal less hassle. It may take 15-30 minuts longer, but you are relaxing the whole time.
Sorry, can't agree with the 2 train option.

You should have time to get the flight. Using the bus is your best bet. Have you tried easy jet or ryanair for LGW to EDI? What about BMI?