As you may be aware, an employer cannot simply change terms and conditions of employment without agreement, particularly where they affect your pay (and particularly against the background of a previous TUPE transfer).
There are a couple of ways you could react to this:
(1) make it clear (in writing) to your employer that you object to the change in your hours and pay but remain in employment and bring a claim for unlawful deduction from wages under the Employment Rights Act 1996, on the basis that your pay has been reduced without your agreement. You would need to continue to make clear your objection until the time of your tribunal hearing, otherwise you may be taken to have agreed to the changes by continuing to work the new hours and receiving the reduced pay.
NB: this is not an easy route to take ... your continued employment is likely to be uncomfortable to say the least and your employer will be doing whatever it can to resolve the situation with you, including dismissing you for failing to accept the changes.
(2) if you are dismissed by your employer or decide to resign in relation to their breach of your employment contract (by reducing your hours and pay) and claim constructive dismissal, my opinion is that you would have a successful claim for automatic unfair dismissal on TUPE grounds. An employer has to have a very good reason (an ETO that is, an Economic, Technical or Organisational, reason entailing changes in the workforce) to justify the dismissal of someone in your position - the fact that they wish to harmonise terms and conditions of employment is not an ETO reason and the fact that the transfer occurred 2 years ago will not assist your employer in arguing the changes are not connected with the transfer if the only reason for harmonising terms is that they have acquired a new workforce who have differing entitlements.
It might also be helpful to know that your employer cannot justify themselves either, should the changes be regarded as being transfer connected, by showing that in relation to some terms you would be better off.
I think it would be worthwhile if you took separate advice on your position frol a lcoal solicitor with employment law expertise. If you go to the Law Society's website (Find a Solicitor section), input your details and you will be given a list of solicitors who you can call.
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