Zen sell ADSL with only a 1 month (ie no) contract.
FTTC is sold with a 12 month contract.
Presumably the £35 surcharge is to exit your contract early.
You could be on the right path here... I forgot about the ADSL
Maybe there are some changed T&C now with Zen, and I'm just not looking properly. However. when I started with Zen in 2015 it was 12 months for the first year of FTTC.
Then it went to a 30 day rolling contract, unless you upgraded to UL fibre 2, and then back down again to UL fibre 1. Also some other permutations of contract, there is a chart on Zen's site somewhere.
I happen to be on a 12 month contract with (about) 10 months to go because I regraded (UL2 didn't work on my line). I would expect if I stayed on it to be on a 30 day contract for FTTC by 2018.
Anyhow I need to talk to Zen about it, but some parts don't add up for me. I'm whining a bit here, but not too much. It's still a good deal and I'm going to take it.
ZeN Unlimited Fibre 1