Tax on rental income in France...any advice??

Hello,
I'm just dabbling in this forum as I'm actually planning to go and live in Australia, but knowing how useful BritishExpats is, I'm hoping someone may be able to answer a question for a friend of mine. She hopes to rent out her holiday property in France and intends to declare the income on her UK tax return (she is permanently resident in England). Is there a double taxation treaty form she needs to get hold of in France and complete, so she doesn't get taxed again there? I guess there is, but not having lived in France myself for over 20 years, I don't know where to start.

Would be really grateful if anyone has time to respond with any suggestions.

Cheers,