No thank you I have all I need. Legally you have not really done anything wrong. You are still an employee of the company and regardless of whether you are on holiday or going though redundancy or raising a grievance, your rights remain unchanged.
If what you did was a normal thing in your job and something that is not out of the ordinary, and also if it was not prohibited under any workplace policy or you were specifically told not to do, then it is not wrong. If the employer wanted to ensure you did not do it then they should have made it clear by issuing you specific instructions to request this. Alternatively they should have included this in a specific policy at work.
Had you left their employment and no longer worked for them and then accessed the system then that would have been a different matter. However, this is not the case here so they are overreacting.
I am also minded to think that there may be an ulterior motive behind this, although it is pure speculation. It may be that if you are potentially being made redundant and they have to pay you redundancy, they could be looking at ways of removing you through dismissal for misconduct by saying that what you did was wrong, thus avoiding having to pay you redundancy. As mentioned it is just a thought but monitor this carefully to see how they proceed and if they are trying to concentrate too much on this. I suggest you simply apologise for what you did, say that you did not think it was wrong in any way as you had not been told not to do it and there was no policy to say you could not do it. If they do try and use this as a reason to dismiss then it could potentially end up as an unfair dismissal and I can discuss your rights in these circumstances if needed.
I hope this has answered your query. I would be grateful if you could please take a second to leave a positive rating (3, 4 or 5 stars) as that is an important part of our process and recognises the time I have spent assisting you. If you need me to clarify anything before you go - please get back to me on here and I will assist further as best as I can. Thank you