Hi,
As per Article 6 of the Italy-UK Double Taxation Agreement, any income received from immovable property in Italy would only be taxable in Italy, however, as a UK resident.
We would advise that the amount received must be declared on your Self-Assessment Tax Return SA106 Foreign supplementary page regardless of the amount, even if a loss has been made, unless the amount was less than £1,000 and you are claiming the Property Allowance.
PIM4702 outlines in further detail rent from property outside of the UK.
Thank you.