Excel issue

I hope someone can help.

I have a shared network hard drive, and all excel files in on of the folders are now only allowing me to read only the files, word, power point are fine.

other folders which have excel files in work as normal, what is this issue and the resolution to this?

Right click the folder and click "Get Info". In the "Sharing and Permissions" section, what does it list for your user? If it says read-only, that's your issue.

Have done this, folder says read only but no options to change, each file within side folder how ever has read/write permissions.

Even if I open file and complete a SAVE AS different filename and version still won't allow me to save it and use it normally

Try this: Open one of the files and do Save As > Options...
Is read only checked? If so, uncheck it.

Also, this is how I found the check box for a Word file: Save As > Options... > Security