France has a high tax base but if you dive into the details it also has significant allowances, IMO far more than the UK that bring the headline level of income tax down.
For example the parts system that can reduce exposure to tax if you have children or dependents living with you, and even the average bloke or blokeess can often claim back expenses incurred, for example traveling to/from work..
Now I'm sure that's going to change but It's pretty much close to impossible to do a compare and contrast, UK v France, especially when it comes to income tax.