You can do it but it would assume that everything aside from say petrol is paid for, and it totally depends on what you like doing.
After me and my gf pay our mortgage and everything else, and by that i mean every single payment for the house we probably have around £600-£700 each a month as 'disposable', you would be shocked at how easily that gets eaten up though and we dont go out much. Birthdays, valentines, x needs sorted this month or y needs paid for this, it all adds ip and whilst you could do it on £250 dont forget if you are paid monthly that when its a 5 weekend month you will have £50 for 1 week.