A lot of French people live in the UK, up to 200,000 in London alone. And yet when it comes to taxes, information is scarce. If you have assets or revenue outside of the UK, some tax maybe due in France or in the UK depending on the asset class. This article tries to explain the rules, some driven by the tax treaty and some by residency. Indeed, the UK residency concept is more complex than the French one: you can be resident and non-ordinarily resident, or resident, ordinarily resident and non-domiciled. And if non-domiciled, again you have the option of being on a remittance basis or on an arising basis.
Residence and Domicile
Those 2 concepts are different in the UK and independent from one another. If you spend more than 90 days in a fiscal year in the UK you become resident. And if you come to the UK with the intention to stay less than 3 years you can get a status of non-ordinarily resident (NOR). That allows you to only pay tax prorated by the time spent in the UK. You have to be careful however to act in a way consistent with that intent. In other words, if you buy a flat, HMRC would consider that your intent is to stay longer than 3 years and they would invalidate the non-ordinarily status.