This was my first time staying in a hostel, and it couldn't have been better. St. Christopher's has a fun and friendly staff, a comfortable feel, and it's really fun!
We arrived at 7 am and couldn't check in until 2pm, but they have a locked room to put your bags in and a chill-out room where you can hang out in, watch movies, play games, etc. Breakfast in the morning was coffee, cereal, and toast, and it's a savior for those mornings when you spent too much time at their bar Belushi's. We met great people, had a blast, slept well, and would go back in a second. We actally booked a hotel for the last two nights in London, spent one night there, and went back to the hostel.
It's located in London's eastside, within walking distance to London Bridge and the Tower of London. The neighboorhood is friendly and we found plenty of great places to eat.