I don't use FB or Whatsapp, I've just tried to install Du Speed Booster, but it says "Insufficient Storage available".......
Sorry for the delay, would you believe my PC just blue-screened! However, it's come back up ok, so back to my tablet. I just powered off and on, and removed several large apps. Managed to get Du Speed Booster installed, and have gone through with that getting rid of lots of stuff. It has now successfully updated 12 apps, so I guess my problem has been solved.
Great stuff, many thanks for your help.