Parallels downloaded Windows 11 Pro but I have purchased Windows 11 Home key. How to downgrade?

Hi All.
New to Parallels and haven't used Windows since 2008.
Downloaded and installed Parallels Desktop on my new 13" M4 Macbook Air.
During that process it downloaded what I thought was Windows 11 Home.
Following the prompts I purchased a product key for Windows 11 Home from Microsoft. I'm only looking for the cheapest option in both Parallels and Windows.
Product Key wouldn't activate Windows. Microsoft says that's because I have Windows 11 Pro installed so need to downgrade to Home.
Is there an easy way to do that?
I've logged a request with Parallels Support but noticed this forum so thought I would join.
Many thanks.
Louis