You have a choice to do what you want to do, but no doubt your friends are all going through the same anxiety. Of course you wouldn't be human if you didn't feel some anxiousness but try and get that into perspective? Is it you being anxious or is it your Mum and family?
You will always be able to come back home any time you want to, we have good transport systems (when they are not striking or repairing) and you won't ever lose your home base and old friends, you can keep in touch always and then just see how you get on.
Your anxiety is normal, everyone is anxious when faced with the unknown, it is scary, but all the new intake at your Uni will be in the same position, you will not be alone. No one will know anyone, that is half the fun. You will gravitate toward people you feel comfortable with and just reassure yourself that if you have found and made good friends at school you will find good friends at Uni
You will face a challenge but throwing in the towel even before you have tried is not the best blueprint to survive life going forward - life is full of challenges that requires courage - just take it a day at a time and give yourself at least six months to decide whether you will fit in at Uni. Most Uni's hold 'freshers' weeks and immerse everyone is link up outings etc so you can find other 'lost souls' to connect with. You will be just fine, .
Go on, get in there and stop allowing your family to worry for you. Before you even know in about 8 weeks or so you will have broken up in November for Christmas!!