You have more than enough left over for food.
But it depends on your other expenses. If you have to use the buses a lot it may not be enough. You may not be able to travel home as often as you would like or go out/ spend as much as you would like.
But £50 a week is more than doable if it's just for food, toiletries and socialising.
You could always get a part time job on the weekend instead of asking your mum/dad for money (unless you're one a course like nursing and medicine in which you already have work placements). Even just 10 hours a week, which is really very little work and should be easily manageable will give you an extra £53 a week. I have friends in final year doing a lot more hours and managing just fine, which means you should really be able to work just fine in first year. You could also work and save up during summer.
And your parents are right, you do need to learn to live on a small budget now. It's better to learn now while you have support around you than learn in 20 years time if something bad happened like you lost your job and you have no idea how to cut back your expenses to live on a tight budget.