Your contract of employment may contain an express term requiring you to move to another location. In some cases such a ‘mobility clause’ may be implied in the contract, for example in senior positions.
Whether an express mobility clause in your contract is enforceable is debatable. If the clause is drafted too widely (e.g. “You may be asked to work at any of our offices in the UK”) or bears little relation to where you’ve worked in reality, your employer may well not be able to insist on the move. Also, if the mobility clause is proportionately more difficult to comply with for a particular category of worker (e.g. part-timers who are predominantly women) it may be regarded as unlawful indirect discrimination.