Do try the new youth hostel on the south downs, just an 1 1/2 on the train from peckham rye to Southease (change at Clapham junction and lewes). Great location, only 5minutes walk to youth hostel and hostel has great cafe (for breakie/afternoon tea) as well as pods outside in the summertime if you fancy something different to bunkbeds. Plenty of family rooms. http://www.yha.org.uk/hostel/south-downs