Just read BT"s email properly.
I have had my present deal since last March 7th so it would be 11 months come the January 7th price rise.
However in the email I found this
"We recommend
Keep your current broadband for the same price you pay today"
If I sign up to a new 18 month deal by the 17th December so as my only rise was £2.50, on my broadband & calls, I can sign up for another 18 months now for the same package at the same price & renegotiate the extra"s I have for free in September 2018.