Just a quick update, hope the following makes sense! as I had recently re-setup my site with a new hosting provider, I had done a brand new install then copied over the relevant SQL files etc.
As my previous old site under www.cymbalroad.com is still sitting with my old hosting provider I did a few more tests there and the inventory levels etc all work perfectly when you make a purchase but it doesn't work correctly on my new site www.cymbalroad.com.au that I had setup on a new hosting provider so the issue must just be with the way I did the install, so I think the best thing for me to do is re do the install and do it really carefully to ensure all the files and folders are loaded correctly as well as the SQL files etc as the test i just did on my old site proved that everything works perfectly.
Once I have the new site setup 100% I plan to just re-direct my old .com URL to my new .com.au URL.
So based on the above I should be able to sort out the issue with a clean new install.