You are having such a teen strop it's silly.
Grow up and GO HOME!
Rather than running away from an issue talk to your mum about it. Say you do not want to go home every weekend. Just once a month.
As for being made to feel guilty when you don't go home on time

. I live at home, i'm 24, my mum still gives me grief and most the time i'm late is because i have a demanding job! Move out of home and get a girlfriend and you'll notice they do the exact same thing when you go out with your mates, get carried away turn up late and a bit siber. HOWEVER if it was you in the same position you'd fine yourself moaning if you are left waiting for someone. So see it from her point of view.
As or your little brothers missing you? Were you not their age once? Can't you be a nice older brother? Surely they must miss you when you're at uni. It's not a big deal.
I've got to say you really need some perspective in your life. Stop acting like a fool. There are plenty of 18yr olds at uni who hav it much worse than you do.
Be grateful for what you have. i had mates whose parents could not even be bothered to drop them to uni or pick them up, they had to shift all the stuff themselves.
You want to grow up...it starts at home.
EDIT:
if you are a complete idiot and need a place to stay.
Search for hostels - tell them you want a long term deal (2months etc)
You should be able to get about £60-70 a week.
Also WHERE ARE YOU USING THE NET?