Isaacs is right in town and easy to find. They have a lot of support for adventurous travelers and good advice on where to go for food, beer, whatever you want. The internet is fast and mostly reliable. My only complaint is that I had a very hard time finding anywhere quiet to have some down time. In the end this is one of the best hostles I've been in.
This was an interesting place. The rooms have obviously been rather recently renovated but the style is like that of 1990s futuristic. The bed was clean, comfortable and bug free; the shower was quite hot; and the room was quiet. The location is pretty bad, unless you happen to want to be in Peckham. For my first time in London, this was a mistake. The Underground doesn't go anywhere near here but there is a bus that will take you to within a block or so. It takes an hour from London downtown
Arty is a good community driven hostle. They have a few activities going on throughout the week, always open checkin, and were easy enough to find (look for the flags). The staff was friendly and helpful to myself and everyone around. They spoke several languages, including very good English.