as my Itunes library has become a mess (thanks Itunes) I decided to format my disc and start again however the format utility has been running for 4 hours now and only at 12.81% and I have an excellent internet connection. Can I stop this and just manually remove the files?
Format utility on a My Cloud? I have no idea what that means. There’s no such thing I’m aware of.
Please tell us exactly how you “formatted” your My Cloud.
If you instead meant that you did a Full Restore, then 13% after 4 hours is not at all unusual if you have a large My Cloud drive.
Under utilities there is a format disc button.