Idoms are expressions in the English language and their meaning does not always realate to the literal meaning of the words.
Here are some common idioms used in the U.K.
1. Barking mad (example sentence - Aya quit her job, she is barking mad!) - This means that someone is insane or acting stangley.
2. Nosy parker (example sentence: Jane was asking where I was last night. She is a nosy parker) - This is someone who is extremely interested in other people's lives.
3. Cheap as chips (example sentence: the ramen restaurant in my neighbourhood is cheap as chips) - this means something is a bargain or very good value for money!
If you would like to learn some more and practice using them in sentences, please check out my 'British English Lesson'.
Have a great day!