Follow @cooldude50's advice.
Complain through Plusnet following the link he posted with all his suggestions added to the complaint. They'll dismiss your complaint and then provide you with a deadlock code (if they say you have to keep the complaint open for 8 weeks before they generate the deadlock code, tell them you've already waited 3 months since sign-up and they'll issue you with one).
Given the number of complaints through CISAS, they might relent and settle your claim there and then, although from my (and @cooldude50's) experience, they'll just give you a long response as to why you aren't entitled to any settlement.
You can then go to the CISAS website and fill out the form for the complaint, adding the deadlock code, and all the questions @cooldude50 posted in a previous post on this thread. Once the complaint with CISAS is filed, it's pretty quick from there. Plusnet has 10 days (I think) to respond to the complaint, during which time they offer you the 110.00 to close the matter.
I had also decided before I complained to CISAS to claim and bank the 50.00 Plusnet cashback cheque (for time spent building this case), so in the end, with the 110.00 settlement I also received from Plusnet, I ended up getting more than I originally wanted when I signed up back in May through Quidco (160 vs 110).
In June when this all started, they could have simply given me the 110.00 and told me I couldn't claim the 50.00 as well (which I would have happily accepted). Instead, most the noise coming from Plusnet reps was rejection and denial of liability.
Go back and see how quickly my concerns were dismissed on page 1 of this thread. It wasn't until I started looking for and dragging other customers into the thread who were facing the same rejection I was that things started to be 'investigated'. And still, with several customers complaining about the same thing, we were still told it was our mistake, not theirs.
All that said, I now have the Plusnet ADSL service almost for free for the duration of my contract (12 months). If the service is decent for the remaining 9 months, I'll consider renewing and actually paying for it with my own money this time, not theirs.
Finally, they really need to tighten up their affiliate presence. Conflicting cashback offers and erroneous redirects should never happen, unless they only have one guy in tech who also quality-checks his own code.
