Yeah, I skipped out on my return ticket from Iceland to go to London instead. It was a hundred and fifty dollars, so why not, I thought.
When I got to London, the passport agent gave me lots of trouble. I'd just finished a fishing season in Alaska, and was fishing. No, I wasn't a student, I didn't have a job in the states, and no, I don't want to work here, I just want to explore, I told him. He didn't like it much, and after I told him a few gracious and innocent lies, he let me loose on London.
Of course, the airline had lost my bag.
That turned into a week in the city and month walking across Scotland, and eventually hitching and hiking up through the highlands to Cape Wrath. It was all south from there, and I'd bought a ticket to return to the states from Ireland, so I had to get there first.
A great counchsurfing weekend in Glasgow and a week of hitching around Ireland later (that was my rule: if I'm not walking, I'm hitching, and vice versa. No other transport allowed), I landed in Boston, broke and inspired, and still a continent away from home (Alaska). With forty dollars in my pocket, it took me two more months to get home.
My advice is to at least get an onward ticket, even if you're not going to use it. I didn't have the money at the time to afford another ticket out of Iceland, and I'm sure it would have been quite a winter indeed if the man in London decided to send me packing back North. Without my bag.