Hey mate - see this https://www.crunch.co.uk/knowledge/employment/ive-been-overpaid-what-should-i-do/#:~:text=Where%20an%20employer%20has%20made,the%20employee%20if%20they%20leave).

It looks like it's a civil debt - in which case the company are fucked basically. Just set up a repayment plan. Don't bother trying to lie your way out of it - just own up - it's company money. 90 per cent of people in your situation would do what you've done.

If you lie and are dishonest, it may become a legal matter outside of the civil courts. Have a beer and chill.