No, don't quote out of context. That's ONLY if you already previously signed a contract with them, and that original contract specifically allowed them to make future updates without your permission.
It's not automatic that a contract is implied, but a contract COULD be implied by action and conduct.
Specific examples where the unsigned contract has been upheld in court: http://www.jordanssolicitors.co.uk/resource/warning-unsigned... http://www.citation.co.uk/news/is-an-unsigned-contract-enfor...