Your contract of employment may contain an express (written) term requiring you work at one of a number of locations. This is known as a 'mobility clause'. Mobility clauses should always be in writing and must use clear language. They should not be hidden away.
An employer should act responsibly and must not breach the duty of mutual trust and confidence when enforcing mobility clauses. For example, it would be a breach of the duty of mutual trust and confidence to insist on relocation to a new office a long way away without giving reasonable notice.
Your employer should take special care to think about groups of workers who may find it harder to get to work in the new location, such as disabled workers, or those with caring responsibilities.
Your employer needs to take care not to engage in indirect discrimination when asking workers to work in a different location, and must not breach the duty to make reasonable adjustments for disabled workers.
Where a union is recognised where you work, your union rep should be consulted by your employer over any proposals to ask staff to work out of a different location, including practical arrangements that need to be put in place. Speak to your rep if you are concerned about the implications for you of your employer's request that you change location.