Am I allowed to live alone at 17 while doing college in the uk?
Ignore the US answers, the word college means something different there. Your problem is going to be that no taxpayer funded school will accept you without proof of parent address in the district so you will need to attend a private school. If the school accepts you as a day pupil, you can work out something with them. I suggest you consider boarding with another family whose child attends the same school as you will not be able to rent a flat alone. Presume you know that A-levels are a two year course so you will need to plan on doing this for two years. How do your parents feel about that? It will be expensive.
Technically; yes. But as minors (people under 18) can't be held liable for legal documents, you will struggle to find any landlord willing to rent anything to you. Assuming you had any way of paying rent in the first place.
Your biggest hurdle is going to be money. How are you going to find somewhere to live? Will the letting agents allow you to rent a place at your age? References? Deposit? Other fees? How are you going to pay for a flat, find the money to furnish a place and pay the bills on this place? Gas, electric, council tax, water rates, TV licence, internet, food, insurance, transport costs, toiletries, clothes, Christmas and birthday presents, college sundries and books, socialising. This is also assuming you have no college fees to pay. And then there will be the loneliness to deal with.
Boarding school. A-levels? You go to boarding school. And go home to mom & dad over school holidays when the school & dorm are closed.
The Oracle of Omigod
I lived by myself right out of high school. My mother got married the week after I graduated and moved a thousand miles away. The main thing is you need a source of income. I worked while I went to college. You also need to get in with several roommates which can be done with online postings at the college.