Variation in English
When foreign learners of English first come to the British Isles, they are usually surprised, and often dismayed, to discover how little they understand of the English they hear. For one thing, people seem to speak faster than expected. Also, the English that most British or Irish people speak seems to be different in many|multiple ways from the English the visitor has learnt. While it is probably differences of pronunciation that will immediately strike them, learners may also notice differences of grammar and vocabulary.
Their reactions to this experience will vary. They may conclude that most of the English, Welsh, Scottish and Irish people that they hear do not – or even cannot – speak English correctly. In this they would find that many native speakers agree with them. They might even be told that, since learners of English as a foreign or second language have usually studied English in a formal way, they should know better than would native speakers what is ‘correct’.