Shockingly, signature is often not actually required in the UK for changes to employment contracts. Sorry I can't find better sources at the moment, but this was recently ruled on again by the UK courts. No signature is required, simply remaining at the job is enough to constitute acceptance in the UK for employment contracts. The employers don't even to show any evidence that you were aware that the contract has been changed.

> Following on from this, a contract of employment does not need to be signed for it to be a binding agreement between the parties as acceptance of its terms can be either verbal or implied through conduct.

http://www.thisismoney.co.uk/money/experts/article-2715470/I...

Add to this, the UK courts are often upholding extremely unilateral employment contract clauses that give the employer the "right to change the contract without the employee's permission at any time." Extremely unilateral power. The UK courts see no problem with it at all. Quite insane.