However, some informal ways to refer to it could be:
* "Five hundred quid": This is the most straightforward option, using the common slang term "quid" for pounds.
* "A half-grand": This is a more concise way to say it, using "grand" for a thousand pounds.
* "Five bills": This uses "bill" as slang for a banknote, though it's less common in London compared to other areas.
Remember that slang can vary depending on the specific group or context. It's always best to be mindful of your audience and choose your language accordingly.