Very dependent on whether you plan to have the mortgage paid off, acquire a new car before you retire, have made sure the house is future proofed (boiler been replaced, roof maintained with a 25yr guarantee etc) and so on.
I’d do a schedule calculating things like annual cost of fuel bills, TV licence, council tax, car maintenance, dental check ups, vet fees, how much you’ve actually spent in the supermarkets in the last year; then add 10% to cover unexpected inflation (another war/oil crisis etc) to get your basic/essential living costs; then I’d add in an amount for holidays, activities (rambling assoc, rock choir, golf club fees etc), annual clothing/shoe spend, hair cuts, make up.
Think you can use templates on line as an aid.
All of these costs will be particular to you - only you know how much it costs to heat your house, which brands/how much you like to spend on clothing, how often you like to get your hair done (once every couple of years for me as I just can’t be bothered until it gets too long).
But once you have this figure you can start planning.