Sch 2 para 9
(1) Nothing in this Schedule prejudices any right of an employee to terminate his contract of employment if a substantial change is made to his detriment in his working conditions. (2) But no such right arises by reason only that (by virtue of paragraph 6, 7 or 8) the identity of his employer changes unless the employee shows that in all the circumstances the change is a significant change and is to his detriment.