Is Paris in your plan? If so Eurostar is an option from London. It is possible now to get a o/w fare for about £51 (which is about the same cost as doing it by easyJet). Traveling by Eurostar is as about as painfree a way to travel between London and the continent as I can think of. You can even get the Piccadilly line direct from Heathrow to St Pancras Plus you arrive in the heart of the city at Paris Nord. Instead of having to schlep in from Orly or CDG.

A mate is coming over from the US in the spring and is flying into London before taking the Eurostar to Paris. Then easyJeting it around before flying back to London.

I would echo others in saying avoid Ryanair unless it really is the only option for you. Most other European LCC's are on the cheap and cheerful side of budget but you do not feel like you are on a flying Greyhound bus. Which in my opinion is exactly what RyanAir is. Depending on your timescale and level of comfort needed look into the cost of traveling by night train. A seat can be as little as 29€ and a sleeper about the same cost as a hotel room . The website www.seat61.com is full of good tips about rail travel. Take a peak also at the Deutsche bahn website and look at City Night Line/ Nachtzug.

One final thing I would say is look at what you are planning to pack and reduce it. Figure out if you really need it. There are plenty of laundromats to be found in big cities so you really only need a very basic capsule wardrobe. In an emergency you can always just do a hand wash in your bathroom sink.