Saw a report today that some roaming charges are slowly being removed by Telefonica/02 (being replaced with fixed monthly charges though):

BBC report

Plus "Spanish ... network Movistar will also bring in the free incoming calls option - ... its Europe-wide service will start immediately."

However, it's doubtful these would apply to prepaid. Manx Telecom (part of Telefonica) has already dropped incoming roaming charges for UK and Ireland, but for contract phones only.