I’m not really sure we know enough about the OP to provide meaningful comment...do we even know if there’s a U.K. connection?
I know relatively little about the French tax system (other than it’s tax return time again
) but I do know that if the OP is permanently employed out of a French airport (i.e. based at one ) the fisc aren’t quietly going to allow him/her to avoid Social Charges by opting for another tax jurisdiction. There might also be other complications if he/she is actually employed by a non French company and is working in France as a posted worker.
(Edit this AM because this just occurred to me overnight)..The OP is referring to their first pay slip .. is he/she new to the French system? I only ask because as many know ATM the France fisc generally don’t do “pay as you go”, I.e. deducting tax etc at source....however personal social charges and tax contributions are assessed in retrospect (tax return) and then you get billed retrospectively (The French the system is about to change to something along the lines of the UK’s PAYE but only for some categories of workers.)
Given the above I’d advise the OP not to spend all the money, bank a fair proportion, and seek the advice of an accountant versed in French Tax law...or failing that if they are brave enough maybe visit the local tax office and talk to someone there to establish the basic principals. (the staff there can actually be v helpful but they will be snowed under at the moment due the aforementioned tax returns....and they were en greve today...at least locally)