This page looks at historic and current migration trends.
Unauthorized Immigrants and Authorized Non-EU/EFTA Nationals Population Per 100,000 in France and the UK in 2017
The chart above shows that the United Kingdom has a far higher percentage of unauthorized immigrants than France. The main reason for this is the loose regulation of the illegal labour market in the UK. This has been cited by France as one of the main reasons for channel crossings which have rise dramatically in recent years.