Fibre Speeds well below what they should be

Hello I am wondering if someone can help me in regards how to deal with TT.

Alittle History, been with TT since 2006, and I have been generally happy with the service, until the last few weeks.  All of a sudden my internet dropped out, and I couldn't connect at all, after resetting the Router a few times, I finally got it back online, and when I did, I contacted TT, and they said I had an issue, and would send BT engineer out to sort it.

Well that turned out badly, and my real issues started, a BT engineer went up the poll, which I could see from my living room, did some stuff, and promptly left.  And oh boy did they leave it in a bad state.  I had to disconnect my router, and then connect it into the engineer socket of my BT box, after much messing about gettin then after much messing about trying, and disbelief, I found out my speeds, had gone from 70mbps download/20mbps upload to 14mbps download/1mbps upload.

I have tried asking them to do "something" about it, that was 7 days ago, now I am out of contract (which I didnt realise), and I like my service, but I am left with the impression that, I can go and screw myself.  Anybody have an idea of how to deal with this customer service cos, I all I get it we are investigating, and yet, my they want there money full, so I want my full service, which I dont think is unfair.