OP as you can see you've asked the ultimate 'how long is a piece of string' question.
Personal spending money on non essentials is right at the bottom of the priority list if you're being sensible, so when deciding what is the right amount what you should look at is:
Pay all bills including rent/mortgage and any debt
Pay all essential child costs if you have DC and make sure you've accounted for irregular spends like gifts and uniforms, possibly savings for university if you're likely to have to contribute to their living costs
Make sure you have a pension
Savings for annual and irregular expenses like insurance, broken cars pets or washing machines and holidays and Christmas etc
Put some money aside in case you lose your income, or buy appropriate insurance
Only after all the above has been covered should you think about what is reasonable to spend on non essentials for yourself or other adults in the house. If there's plenty left, you're fine, but if there's little or nothing left, you need to see what costs you can cut to free money up.
Think about everything you spend. Some things are fairly fixed and essential, eg council tax or water others there's a huge variation in what you have to spend and if you're spending a lot more than the minimum there's scope to cut down.
Eg is your grocery shopping £50 pw in Aldi or £200 pw in Waitrose. Is your phone sim only with a £150 Android replaced every 3 or 4 years, or £60 pm for a new iPhone.
Is your car on a PCP that costs hundreds of pounds a month or do you own a second hand car outright? Some people spend £100+ pm on beauty etc, others next to nothing.
How much do you spend on coffees, lunches, eating out, again some people spend hundreds of pounds a month, others far less etc etc etc.