I'd suggest making a list of the things you will need/want to pay for and coming up with a figure for each, as things will vary by property/area;
- Council Tax
- Water
- Gas/Electric
- Broadband
- Food shopping
- Travel - do you have a car, or get public transport etc?
- Mobile phone
- Contents insurance
- TV license or Netflix/other TV package?
You can check the council tax bands of the kinds of places you're looking to rent here www.gov.uk/council-tax-bands, then google [your local council name] council tax bands to get the amounts, e.g. South Tyneside is here: www.southtyneside.gov.uk/article/56091/List-of-Council-Tax-bands. Remember you'll get 25% off for living alone. As a rough ballpark figure you're probably looking at about £75-£100 a month but it'll depend on how big a place you get and which council you live in.
Gas and electric can vary a lot depending on property type. If you're in terraced or a flat with other properties around you your house will retain heat so you won't need the heating on so much. And age of property makes a difference to how well insulated it is. I used to pay about £35 a month in a new build terrace, but have also paid £75 in an older semi detatched bungalow about the same size! So maybe that might influence your choice of what kind of place to rent.
My water bill has fairly consistently been about £25-£35 a month.
Our broadband is £22.50 a month for a fairly good package but I'm not sure if you could get a limited service for cheaper.
Food shopping will depend on what supermarkets you have available and whether you are a good cook or rely on convenience food a lot. £30 a week should be doable if you aren't fussy.
And don't forget to budget for items you'll need to set up your home. You might rent somewhere furnished but you'll need to buy some basic kitchen things such as plates, kettle, saucepans, cutlery, bedding, towels etc if you don't already have them. If so don't forget to budget a chunk of money for that on top of the deposit you'll have to pay for the flat/house.
Good luck with the move OP and good on you for escaping from your parents.