Hi, So sorry for your loss.
I used to work in HR and I think the problem is that a lot of Managers don't properly explain things to their staff!
The meeting isn't a disciplinary, it's a sickness absence review.
Don't worry about all the letters and meeting - this is, as others have explained, documentation that most employers have to fill in - usually at a trigger point, which allows them to continue to pay your sick pay.
The Union Rep reference is a legal requirement, not a threat.
A lot of stress and upset could be avoided if managers had the forethought to just say to their employees "This isn't a disciplinary, it's a meeting that we have to have to look at your recent sickness. It's just to make sure everything's alright, and we can support you if you need it and make plans to keep the service running if we need to".
Of course some people abuse the system, but most don't to be honest.
I used to work in HR and am a few years out of date, but iirc, UK employment law states that a MC after 24 weeks is classed as a stillbirth and standard Mat leave requirement kick in. Therefore, most companies (in lieu of further guidance) usually have to manage a MC under 24 weeks under existing sickness policies.
I agree that it's insensitive and should be changed, but it's not an intentional on the part of your employer - unfortunately they are acting under the only guidelines they have.
As for this week? Follow your doctors advice. Get a sick note (explain your situation to your GP if need be and I'm sure they'll help).
Don't make your health worse by struggling in when you shouldn't because of this policy - you need to take care of yourself and if you don't rest and get well when you should, you risk making yourself worse and ending up taking more time off work! You know you are not abusing the system, and actually, I'm sure they do too. I know how hard it is for teachers to be off (DM and DSIL are both primary school teachers) but you can't help this.
Please take care of yourself!