According to a stat I just saw, in 2017 14.4% of the UK population are foreign born.
Is that a lot?
Lol.
What I mean is it above average or far more than other countries?
It is around the same as the USA; less than Canada and Australia. Switzerland is higher, Luxembourg is much higher (about 50%).
I remember reading Japan was pretty low (just checked, it is a bit less than 2%).