I seem to remember that TT's Minimum Term was 18 months originally, like when you joined, and has only reduced to 12 months in the last few months.
They say if we want to now leave we will have to pay at least £70.00 just to get out of the 18 month contract.
However, you should not have to pay £70 to get outta contract. Ofcom reduced these cancellation fees in June 2010 see:
Cheaper charges for UK consumers to end phone contracts for your package.
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU BB => 2010: Orange 19 Meg Tweaked / 16 Meg Untweaked LLU BB