Big Ben Switcheroo

London is the cheap airfares turnstile of Europe, so fly cheaply into here and then elsewhere in Europe or North Africa on a no-frills airline for far less

London is usually the cheapest European city into which you can fly from the U.S. 

London is also the main hub for Europe's great no-frills airlines, connecting the capital of the British Empire with the cities and vacation spots of Europe, North Africa, and the Middle East for as little as nothing (Ryanair often runs "free" sales—though it also tacks on the most ancillary fees) to maybe $120 max. 

Add those two facts together, and you may be able to subtract hundreds of dollars from your airfare.

If you don't mind doing some fancy footwork, booking everything yourself, and hauling your luggage around a bit, you can take advantage of this confluence of budget travel truisms to do what I call the Big Ben Switcheroo.

Here is a practical example, using a sample trip taken from New York, pitting fares gleaned from Expedia against the Big Ben Switcheroo (using a keen $170 roundtrip to London, which was actually available as I wrote this).

NYC to:	Expedia	Switcheroo	how?	savings
Rome	$342	$210	($22 fare on Ryanair)	$132

The great thing is, though, this way you're not limited to round-trip flights. The Switcheroo is also a fantastic way to arrange a trip that starts in one place and ends in another, since no-frills tickets are always priced one-way. That means you could, say, fly from London to Madrid, tour your way across Mediterranean Europe by a combination of means (trains, more no-frills carriers, rental car, whatever), then fly back to London from Rome—or wherever it is you end up.

The Rules of the Game

1) First, find a cheap fare to London

Go through the steps for getting the cheapest airfare. » more

2) Check out all the no-frills and low-cost carriers

See which ones fly to the city you want to visit. Ryanair and easyJet are the obvious ones, as they're based in London, but don’t forget to "reverse-hub" your logic—Eurowings may be based in Dusseldorf, but it flies to London from there, so if Germany is where you want to be, check their flights out, too. Remember: no-frills tickets are one-way, so there's no need to book both directions with the same outfit. You could fly easyJet out and Ryanair back, and neither would be offended. » more 

3) Figure out the "Switcheroo" portion in London

Most transatlantic flights land in Heathrow, or sometimes Gatwick, airport.

Most no-frills use Luton or Stansted airports—though easyJet uses Gatwick as well.

You're either going to have to shuttle between London airports (easiest by a long shot, but there may not be frequent service), or make your way downtown London from one airport and then back out to the other airport. » more

This is where the technique gets annoyingly time-consuming. There are now transit services between each airport, but not all are conveniently timed (plus, to make air schedules match up, you may actually have to spend the night in town, so you'll be transferring via downtown London):

1. Retrieve luggage
2. Haul luggage to bus/train/car to connect airports
3. Ride to other airport (or if you are transferring via downtown London...
   1. Haul luggage down into Underground to switch from the downtown station where you arrived to the one where you can get transport out to the other airport
   2. Ride Underground
   3. Haul luggage up to means of transport out to other airport
   4. Ride to other airport
4. Haul luggage to check-in
5. (Notice the high degree of "hauling luggage"; See "The fine art of packing light".)

4) Factor in the additional expenses and time to switch airports

This page on Getting between London's airports details the option, prices, and travel times for the fastest and easiest links with and between London's airports—though note that some "convenient" direct connections might run infrequently, such as Heathrow/Luton, which goes only every two hours. » more

5) Allow yourself at least a 4–5 hour window between flights (more from Gatwick)

That should cover travel time between airports, the need to check-in an hour before your ongoing flight, plus a 90-minute cushion in case your first flight lands late.

Know that no-frills schedules tend to fall behind schedule more often than major airlines, so allow a slightly longer time cushion between that no-frills back to London and the flight home. 

6) Realize this might means you end up stuck in London overnight

Sometimes, the schedules just don't match up properly—usually on the way home (your flight from, say, Pisa arriving too late in the day to hook up with your return transatlantic flight).

This is not a problem if you planned to spend some time in London anyway, but if Big Ben is just a turnstile for you, this extraneous night can be a financial burden—London hotels are expensive!

The Upshot

I’ve done this rigmarole of switching over to no-frills once on British soil myself a few times. I don’t mind the effort to save a few hundred bucks, but some people find this DIY method too annoying and nerve-racking.

Please don’t forget to factor in the time involved—and aggravation of schlepping luggage—to get between airports in London before deciding to try it out. 

And remember: since you're your own travel agent, ain't no one gonna bail you out if you get off schedule. If one of your flights is delayed and you're not going to arrive in London in time to catch the next one, the other airline couldn't care less and will fly without you. As far as it's concerned, you missed the plane.

That's a risk you're going to have to accept—and a good reason to pad the Big Ben Switcheroo plan with an extra day in London on either end, just to be safe.