Changing package mid contract

[#1]

Hi
I have just subscribed to fibre on an 18 month contract with a 40GB download limit. It is proving quite a hit with the family. If this continues can I upgrade my package to unlimited during the initial 18 month contract or would there be an additional cost (over and above the monthly unlimited charge)?
Thanks in advance for you help.
Regards
Andy

[#2]

you can upgrade but you would lose any outstanding price reductions and may - I am not sure - start a new contract

[#3]

You would definitely start a new contract and if you just did it on line you would lose any current discount/introductory offer. Probably bet to ring up and negotiate an upgrade.

[#4]

According to the support pages at http://www.plus.net/support/broadband/products/change_broadband.shtml you don't have to start a new contract if you are moving from a current fibre product to another current fibre product:
"Residential customers
If you’re Essentials or Unlimited, you can switch between products of the same type (standard broadband to standard broadband or fibre optic to fibre optic) for free without affecting your current contract."
It's only if you're moving from standard broadband to fibre or from a legacy fibre product to a current fibre product that you would need to start a new 18 month contract.