I have been on broadband for 6 years now, and changed ISPs 7 times on adsl. I have had experience with ones like Zen, Newnet, Entanet NDO, not rubbish. TalkTalk compares well with them in regards to speed and reliability. As you may expect p2p will be slower, but is still very usable!.
I have had no need to use support on any service, but I tried on TalkTalk when I had a minor issue and support was 1st class. If 40GB a month will do you why kid yourself and pay more?.