Well, any rules regarding tax will probably apply to most countries, especially the European continent. The general rule of thumb is that you declare your income in the country that you reside. As long as the money you're earning is from legitimate sources, I don't see an issue.
The UK government won't complain about receiving tax from a foreign source of income, and the French government can't prevent companies from outsourcing work to freelancers from other countries. Even if the French government punishes them with some kind of tax embargo, it will be theirs to pay, not yours.
Edit: Here is some more information that you may find helpful, so far no one has voted to close it: UK freelancer living in Thailand working for UK based clients...tax?UK freelancer living in Thailand working for UK based clients...tax?