Many thanks for your patience, I am pleased to be able to continue assisting with your query now. I am not sure what Government regulations the employer is referring to as allowing them to change the contracts as and when they wish. They may have been able to make some changes to reduce the mixing of people, such as ensuring the shifts are not staggered toom close to each other to reduce the probability of too many people being in the same place at the same time. However, these changes are unlikely to have bene permanent and would have only been dictated by the necessities at the time, so once these are no longer needed, they should resume to your original contract. I do not see that you have a legal right to remain on 35h a week if the changes were simply temporary in response to the Covid situation.
If you still wanted to challenge the employer you can do so through a grievance, perhaps as a group. You can get a detailed explanation of the grievance process here:
In summary, an employee is expected to submit their concerns in writing and send them to their line manager, or whoever is nominated as the person to send grievances to under an official workplace grievance policy.
The complaint should include details of what the grievance is about, any evidence that may exist which is relevant and also what the employee wants their employer to do about this issue.
Once the grievance has been submitted, the employer is expected to arrange a formal grievance hearing, inviting the employee to attend and discuss the nature of their complaint. The meeting is also as an opportunity to ask for further clarification or information, as required.
Following the meeting, the employer will take time to consider all the issues and evidence and then make a decision, communicating it to the employee. If the outcome is not to the complainant’s satisfaction, they can appeal and get a second opinion from a different person assigned by the employer to consider the appeal. Once the appeal is also completed, that brings to an end the formal grievance process and there is no option to escalate it further internally.