Twinkie1 it sounds as though you shouldn't be in work so don't go.
If you are able to work from home and it's just the journey, then you don't need to be signed off sick, and I would advise you don't get signed off sick as such.
Does your employer have occupational health advisers? If so, I would advise you ask to speak to one, and get them to write a recommendation that you are fit for work, but only to work from home. That way you are not 'off sick', you aren't on sick pay or adding to your sickness record but you are getting the recovery time you need.
If you are properly signed off sick, that means don't work and your employer shouldn't let you do so.
If there is no occ health, I would consider asking your GP to write a similar recommendation for your employers.
Regarding the redundancy, they may have decided already who is going, without knowing how far down the process they are, difficult to say. Either way, the criteria they are using for selection for redundancy ought to be made very clear to you. Attendance record can be one of those criteria. However, it would be wrong to say that occasionally if an employer knows exactly who they want to keep and who they want to get rid of, and they wouldn't bear this in mind when designing their criteria grids, iyswim.
If your general performance and attendance is good, you have skills and experience they need, then a period of absence for one defined medical procedure shouldn't hinder you. Your absence record is more likely to be an issue if you are one of those people with a tendency to suffer from 'headaches' or 'tummy upsets' on a Monday morning.