Transport, and Accomodation for Wireless Festival, Hyde Park?

A few of us have booked for the Wireless Festival for Friday 1st July. We live up north in the Lancashire area, so don't know London that well. Was just wonder if anyone could recommend a good, clean, cheap hostel in the Hyde Park area? Also what would you say is the cheapest/easiest way of us getting too Hyde Park from up North? Train/Coach? Once in London, Taxi/Buses/Tube?