If I upgrade when I have 6 months left on current plan will I be charged for the both
No. Not if it is an upgrade on what you have. You will only be charged for the upgrade package once it starts.
Thanks
It's from fibre 1 to the halo
I get poor Internet were I am with the fibre 1 so thought by upgrading I might get better Internet connection
Halo is not actually an upgrade but an add-on which may result in the start of a new contract. If there is any chance that FTTP will be available in near future then I wouldn't bother with Halo
If you can't get Fibre 2 then Fibre 1 might be the best you can get until FTTP becomes available.
Halo WILL NOT improve your internet connection, it is just a benefits package.