The British slang for going to the bathroom is "going to the loo".
This phrase is widely used in the UK and is considered a more polite and less formal way to refer to using the toilet.
Here are some other common British slang terms for going to the bathroom:
- "Having a wee" - This refers to urinating.
- "Having a number two" - This refers to defecating.
- "Going for a slash" - This is a slang term for urinating, particularly for men.
- "Going for a pee" - This is another slang term for urinating.
- "Taking a dump" - This is a less polite slang term for defecating.
It's important to note that the level of formality and politeness of these slang terms can vary depending on the context and the people involved.