It's very much a 'how long is a piece of string' question.
What are your lifestyle expectations (holidays, where you do your grocery shopping and what sort of food you buy, what you spend on personal grooming and clothes, how often you eat out and where, what you spend on cars, gadgets etc).
The amount people spend on the above will vary by hundreds, if not thousands of pounds a month depending on how much money is available and what people actually buy/do.
There's also the consideration that if you're more towards the lower spending end of the spectrum, this gives you the freedom to work less and/or retire earlier, if that's something that's important to you.
Also percentages don't mean much because the amount of money that a certain percentage is varies enormously depending on how much you're talking about, eg if your income is £2k per month and you save £200, that's 10%. If your income is £10k per month and you save £500, that's only 5%.