Flipping through that quickly (Dom, it's "fewer people", not "less people" - picky, I know..)..
The guy in the restaurant did not have a five year contract. He had a 60 contract. Yes, just 60. Not 60 months. It just said "60". So he could simply infer that to mean 60 days as he wishes. It is a fundamental requirement that terms are clearly presented, and this was not. So it was never enforceable. Nice try of BT to slip that in to the small print contrary to the verbal agreement, though.
Secondly, the bit in the Ts & Cs which says that BT can change the services or charges at any time is unlawful (Business to consumer) and so the consumer may safely ignore that. Any harrasment by debt collection agencies is easily stopped by simply sending a letter back to the debt collection agency stating that the matter is in dispute and that the customer will not take any action until the dispute is resolved, and any further contact will be considered harrassment. Plenty of template letters available on the internet to download. Should said DCA continue contact, this is potentially quite a serious offence.
Any contract which is supposed to run for two years is unlikely to be able to be held to term for two years simply because at some stage the provider is likely to want to change some aspect of the contract, at which point the consumer may exit without penalty.
Sadly, few understand this, and it appears that OFCOM is quite happy for BT to issue unlawfully worded contracts unless enough people complain. And when they do, OFCOM does not appear to have the necessary "teeth" to fine on a "set an example" basis.
I've never known any other company, with the possible smaller-scale exception of Ryanair treat its customers with such contempt that they literally would never go near it again under any circumstances.