Here is what TIMATIC (IATA) provides for a UK national & resident departing from the UK to Italy without connection and not having traveled elsewhere in the past 6 days. OP will need to answer the questions as to his passport & its endorsements.

The bottom line is that it always pays to have a full printout of what the agent will see. They err on the side of caution.

Passport required.
- Passports and/or passport replacing documents must be valid
for at least 3 months beyond the period of intended stay.
- British passports endorsed British Citizen must be valid

on arrival.
- British passports endorsed British Subject which also

contain a Certificate of Entitlement to the Right of Abode

issued by the United Kingdom, must be valid on arrival.