Surprisingly, there is no law declaring English the official language of the UK.
In fact, English is just the de facto official language of the UK, which means it is not legally sanctioned as official but spoken by the majority.
England and Scotland do not have any official languages. Northern Ireland’s official languages are English and Irish.
Doesn’t sound right to me. As someone living in Scotland, my understanding is that the Scottish Government recognises 4 official languages: Scots, English, Gaelic, and BSL.
Edit: Wikipedia lists those 4 as official languages in Scotland https://en.m.wikipedia.org/wiki/Languages_of_Scotland