I think that your permanent home is counted as wherever you're registered on the electoral roll, which is why you're always encouraged to register on the roll with your uni address. Technically, you're going to be spending *most* of your year at uni anyway and I think it's worked out by where you spend most of your year, uni is generally 36/8 weeks and I'm not sure if the 14/16 weeks you get as holiday is enough for your home to be counted as a permanent residence. I don't think that you can legally have more than one 'permanent' address. Also remember that you're over 18 so I think it goes off where you're living 'now', rather than the parental home being automatically assumed to be your permanent address.
Also, in student terms it's the property that's exempt from council tax. A student house (where only students live) or halls is automatically exempt and so are the people in it (providing they fit the 'student' criteria).
I can't honestly see that it's going to make much difference to the amount of council tax that you pay at home anyway. If you live with a single parent they'd become eligible for the single person's discount (25%) providing of course that there isn't another non-exempt adult living at home eg a working adult sibling, but they'd be getting that discount anyway until you turned 18, and they'd still get that discount anyway if you stayed at home, since as a student you'd be exempt. If everyone in your household was 'disregarded' for c/t purposes they'd be getting a 50% reduction, but again you being a student and staying at home wouldn't change that, and neiter would you leaving. It's all a bit complicated lol ...