My evidence is from living here. There is some immigration - but mostly in urban areas. In Highland, Argyll, the Islands, Shetland, Orkney, Perthshire, Angus it very much is not the norm. Compare Glasgow with London, or even Manchester or Birmingham, and it remains far whiter and more "Brit / Scot"
My school has only twice in 25 years had non-White pupils, both siblings (Asian Mum, British Dad) and we have 2 pupils from Europe who arrived in the last year. That's it! Exotic means born in Wales, or England.
Manchester is 66% white, Glasgow 88%. From 2 different websites but roughly correct. Dundee is 6%.
Rural areas close to 0%.
I just don't see the immigration debate being had here - not because we are less racist, but because we haven't encountered it on the scale there is in parts of England.
But, the main reason is we have always blamed Westminster, not Brussels.