Taken from easy jet web site:-
Whether you're travelling within the UK or abroad, you must be able to identify yourself at check-in. But bear in mind that not all kinds of photographic ID are accepted. You can take any one from the list below, but remember that if you are not able to present one of these forms of ID at check-in, easyJet cannot accept you for travel.
UK domestic flights
A valid passport - an expired passport can be used up to a maximum of two years after expiry
Valid photographic EU or Swiss national identity card
Valid photographic driving licence
Valid armed forces identity card
Valid police warrant card/badge
Valid airport employees security identity pass
A child on parent' s passport is an acceptable form of ID
CitizenCard
Valid photographic firearm certificate
Valid Government-issued identity card
SMART card
Electoral identity card
Acceptable form of non-photographic ID:
Pension Book
Children under 16 years of age travelling on UK domestic flights can travel without photo identification provided that they are travelling with an accompanying adult.
International flights