Depends whether they want employees who are loyal and prepared to go the extra mile for the company and the customers. Or employees who feel aggrieved and take every opportunity to exploit and abuse the system. You reap what you sow.
You know what, some will feel annoyed. Others will just shrug, and get on with it. Others will celebrate as it will mean they can get to work more easily than before. Every relocation I've had, there's been winners and there's been losers. First time it happened to me, I got a commute that was five minutes longer (company consolidated sites). Second time it was reduced by 20 minutes (company moved to bigger premises.)
In both cases, the employer did the maths. They looked at where its employers were based. What was their likely travel time, travel costs. They tried to soften the blow by offering assistance to those whose travel costs were impacted negatively by the move. There are ways to soften the blow. There are things that can be done.
But the fact of the matter is that most - if not all - of those staff will have signed a contract with a mobility clause in it. A clause that says they agree to a move like this. A clause most of them will have agreed to before starting the job.
You can find a copy of the Royal Mail's seasonal worker engagement contract online at
http://www.royalmailgroup.com/sites/default/files/Christmas%20Casual%202016%20Terms%20Of%20Engagement%20V1_0.pdfHere's its mobility clause:
Your initial place of work during any engagement will be shown in your offer
letter. However, the needs of Royal Mail require mobility. During any period of engagement therefore, you may be required to work elsewhere other than at your initial place of work. You will not be required to work outside the UK in the course of your duties. It's gloriously vague. But it's there in black and white. This is obviously a seasonal contract, but I'd put good money on the standard contract being similar.
The only recourse someone has here is if they can prove the request to work elsewhere is completely unreasonable (see
https://www.gov.uk/employer-relocation-your-rights).
i.e. Royal Mail telling staff in Marple that they must relocate to Oban in the Scottish Highlands is probably unreasonable. Telling them they need to go to Stockport, isn't ever going to be so.