So if you added another person you'd need to charge them £250 then? Is that what you're saying @coffeeaddict77?
What if they ate more than you? Or different stuff to you? And the shopping bill went up? What if they cooked more than you?
What if they took baths more than you? Took much deeper baths than you? Stayed in there for ages topping up with hot water? Showered in the morning AND took baths at night?
What if they were at home using energy more than you? Or at different times to you so the heating was on for more hours. What if they liked the heating up hotter than you do? Used the dryer more than you do? Did laundry more than you? Changed their towels and sheets more often than you,
Had a visitor round eating and bathing about 12 days a month?
What if the person left things running and using energy more than you do,
What if the home in question is bigger than yours, draughtier than yours? And costs more to heat than yours?
And you lost the single person discount on your council tax?
It's £500 a month for you two to live exactly as you do. Other people's circumstances vary and lots of little additions mount up.