Well, @Mick I am afraid but this gives me a feel that you may require to flash the stock ROM again over to your device 
to begin with make sure that you have installed all the the device drivers and
Perquisites(Downloaded over to your PC/Laptop):
1.Get the appropriate version of stock ROM, according to you region from "sammobile.com/firmwares" section.
2.Get the Latest version of Odin
Installation Process:
1.Switch off your Tablet and boot Galaxy Tab into Download Mode by pressing and holding the Volume Down and Power keys together until you get the warning message, now press Volume Up key to proceed to Download Mode.
2.Extract the downloaded Odin zip file and run the Odin.exe file as an administrator.
3.Connect your Galaxy Tab to your computer via USB cable.
4.In Odin screen, you should see a COM Port number like “0:[COM7]” at ID:COM section and “Added!” text at the message box. It means that Odin has detected your device and you are going great!
5.Make sure that, the “Auto Reboot” and “F. Reset Time” options are checked.
6.Now, extract the downloaded firmware zip file (the one you downloaded at the very first step of Perquisites), you’ll find a firmware file with extension.tar.md5
7.In Odin screen, click on PDA button and select the firmware file with .tar.md5 extension.
8.Now, click on the Start button to begin the installation process, wait few moments.
- If everything goes in a correct manner then, you would see “PASS!” message in ID:COM port having green background !
10.Your Tablet should automatically reboot after completion and you can disconnect the tab from PC.
See if this can help you out ! 
— modified on Nov 11, 2014, 8:15:10 AM
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