I did that many years ago...all under 20 for hostels. I took a bus from London to Rome for about 200 dollar. I then took a flight from Nice back to London which cost almost nothing. I didn't know why the flight was so cheap, a Chinese girl told me that in a hostel. the flight from Ottawa to London was under 600 round trip. my total cost was under 2000 or 3000? I forgot which...