[DanBC]

Kazuo Ishiguro is British. He's not called "Sir" because he has an OBE. He needs a GBE or DBE for the "Sir".

https://en.wikipedia.org/wiki/Order_of_the_British_Empire

[OJFord]

And were he not British, he would not be entitled as such - Gates and Geldof iirc are such examples; sometimes (incorrectly) titled 'Sir' in press.