thanks again Jason
After your last message, and looking at the debug code, it was apparent that the problem lay in the uploaded image location.
I prefer using absolute rather than relative file paths and this is where the problem occured for me.
As I am working within an admin folder, then the line
'UploadFolder' => "../images/" is working OK
With an absolute file path, if i try to use 'UploadFolder' => "/images/", i get a string of error messages.
I must have dropped the leading slash before saving the file last time, which would obviously result in the file path /admin/images :)