It seems even tho the 50mb modem can handle the speed you will need to take the new superhub and pay the installation charge along with the activation charge.
Cant remember what the installation charge was when i took out 50mb.
£40/£50 I think and I wont be paying for that again.

I live in the real country side 

Do you have to register interest?
I hope it will be something similar to the 50mb price.