Thanks for your patience. The main issue here is going to be your length of service. If you have been continuously employed at your place of work for less than 2 years then your employment rights will unfortunately be somewhat limited. Most importantly, you will not be protected against unfair dismissal or constructive dismissal. This means that your employer can dismiss you or force you to leave for more or less any reason, and without following a fair procedure, as long as their decision is not based on discriminatory grounds (i.e. because of gender, race, religion, age, a disability, sexual orientation, etc.) or because you were trying to assert any of your statutory rights (e.g. requesting maternity/paternity leave, etc.).
So you can find that they do not act in accordance with your contract in terms of changing the terms. This cannot be challenged unless you have suffered losses, such as for example they did not pay you what you were due under contract. However, if they changes your role, location, responsibilities, etc then that would not be challengeable until you have at least 2 years’ service. So what they have done is immoral but not illegal and whilst you can challenge it internally, you will not be able to take any legal action against them.
I'm sorry if this is not necessarily the answer you were hoping for, however I do have a duty to be honest and explain the law as it actually stands. This does mean delivering bad news from time to time. I hope you understand and would be happy to provide any further clarification if needed. If you are still satisfied with the level of service you have received I would be grateful if you could please take a second to leave a positive rating by selecting 3, 4 or 5 starts at the top of the page. Thank you