Well even if the union takes it up, they will be "rocking the boat" because it will be clear who has complained to the union. The union can't just tell the employer that anonymous people don't want to return to the office or want to work in the office less. They'd be laughed out of court, because it isn't up to the union or employees to tell the employer where people generally are willing to work from. In other words, it doesn't matter whether there is a business need in your opinion or not - the employers opinion about where they want their employees is the only thing that matters. And I am not saying that to be unhelpful or unsympathetic - but the pandemic seems to have altered some peoples perception of who is in charge in the workplace. There were far too many articles flying around about how nobody was ever going back to the office, and those have set up an expectation that is entirely unrealistic.
On the specifics, the individuals would have to submit a grievance. The one of crutches – no they are not covered by the Equality Act (which “covers” significantly less than most people think it does). To be considered disabled you must have a physical or mental impairment that has a ‘substantial’ and ‘long-term’ negative effect on your ability to do normal daily activities and which has lasted or is expected to last a year or more. So realistically, that person can ask for some flexibility but cannot insist on it. The second individual perhaps may have some leeway if their condition fulfils the criteria, but again, they must formally ask for reasonable adjustments. And they need to be cautious – if they are saying that they can come into the office at all, then they are on shaky ground because one day a week is no more unreasonable that one day a fortnight. They can either come in or not. And if they cannot come in at all, that might bring into question their capability in the role – as I said previously, the fact that employees consider that there is not business need to go into the office doesn’t mean the employer has to agree.
And, to provide some balance, there are reasons why an employer might want people in the office that have nothing to do with whether you can do the job from home. Person to person contact, team building and the like are simply not as effective digitally. Offices have to be paid for so there is little point in having an office that is more often empty than not.
And sometimes you have to pick your battles… if these people get this, won’t everyone else want it too? Or are you trying to use this as a wedge for exactly that reason? Because unless you are confident of winning, you could provoke a worse response than you already have – there is absolutely nothing to stop the employer saying that you will all return to the office 5 days a week, and anyone who physically can’t should be signed off sick.
If they still want to take this further, then a grievance is the only way to go. Either the individuals must submit a grievance on their own behalf (with union support if they are members); or, if the actual issue is that you all want to be in the office less, it’s a collective grievance which the union can take forward – but you need to ensure that everyone is on board (including non-union members) and is ready for any fall out that might ensue.
In all honesty, speaking as a manager, I think on the face of it your manager may be being unreasonable, and I would personally be much more flexible – but they may also have good reasons why this is their policy. And I’m a manager who primarily works from home because I am disabled!