Several weeks ago, I promised a UK DCC receipt from an ATM. Here it is...
Exchange rate of 1 GBP = 1.4965 EUR.
So withdrawing £100 on the same day, using the indicative FX rates on the respective card issuer sites:
ATM rate €149.65
MasterCard €139.79
Visa €139.98
Quite a hefty difference there if your card issuer does not charge for overseas withdrawals.
On a positive and unrelated note, I would say Italy is very DCC free. Over the last three years, I have travelled to Bergamo, Trento, Venice, Milan, Bologna and Rome. All types of businesses used (including those with handheld terminals and those integrated into POS). Only one place has offered DCC, which was a chain hotel in Milan. It was well advertised and offered by the staff. Nowhere else has offered DCC.