My Parents wont let me travel on the train on my own!?

I want to go visit friends, they live about 2 hours away from me.
They came to visit me on a national express coach, However, there are none that leave in the morning going the right direction for me.
There are however lots of trains, but my mum doesnt want me to go on my own becsuee she doesnt think i will manage the changes at "London Liverpool Street".
I think that i am 15, and need to be given some responsibility! I cant be kept in cottonwool forver.
How can i get my mum to come around to the idea of me traveling alone?!

try going on something other than a train. they may let you go