Hi IfanJamesBU!
I'm Jen, an independent advisor and a Microsoft user like you. I'd be happy to help you out with this issue.
The sizes of the horizontal and vertical scroll bars are normally determined by the dimensions of the used range. Here's an article that provides a few work-arounds on how to fix this.
https://exceloffthegrid.com/resetting-the-scrol...
Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.
I hope this information helps. If you have any questions, please let me know and I'd be glad to assist you further.
Best Regards!
Jen :)