I've dug around in past discussions but am still bit confused on how best to prepare for this. We have a 1st Class flight from Los Angeles to Heathrow as part of a trip to Spain in December. Our flight from the UK to Seville departs from Gatwick. We have about 4 hours between the flights.
How does this impact going through customs? Will it make a difference if we have checked bags? Do our 1st Class tickets make a difference?
What's the best way to get between the airports? Taxi? Shuttle bus mentioned on the Heathrow website? Subway?
Any other tips or details I haven't thought of?