Jersey doesn't require UK citizens to present a passport in order to enter the island:
http://jersey.com/eng...ms/pages/default.aspx
However, if you're flying there, you'll need some sort of photographic ID for security purposes. Some airlines (e.g. easyJet, who operate to Jersey from LIverpool) will accept things like bus passes, whereas others will only accept a passport, a national identity card or possibly a driving licence. If you're unsure check the relevant airline's website or post again here, stating either the airline you'll be travelling with or the airport(s) you're considering travelling from.
Chris