Before the appointed call I fixed it myself. I will recount the procedure in case anyone comes here looking for a solution to this problem.
Established the problem; when the iPad became un-paired with the MBL and then floundered around while I tried to re-establish it on a new network with no internet connectivity it tricked itself into thinking that it was in the hands of a developer. My Apple account was then frozen for the iPad only. A message came up saying that I needed a “sandbox” account. The specific problem was, I think, that the WD2go app always needs to connect to WD servers on the internet even to link local mobile computers to the MBL.
The first thing I did was use the WD control panel in a local web address to un-link all my mobile devices from the MBL. I left all the shares alone. I was unable to re-link on the new network with WD2go without internet connectivity. My Apple account still worked on my iTouch. I noticed that, even though my account was frozen on the iPad, any apps purchased on the iTouch synced to the iPad automatically. I downloaded an app called File Browser to the iTouch which also appeared on my iPad. I established that File Browser was able to connect my iTouch to the MBL on the new network without internet connectivity. I then used File Browser to re-link the MBL to the iPad. Care was taken to use the same password to the device, user name, and password that were established with the WD2go app on the original network. This gave access to everything that I loaded onto the MBL on the original network including private shares.
It turned out that, by re-establishing the link between the iPad and the MBL, the iOS on the iPad saw the error of its ways and everything is back as it should be. I can easily switch between the network with no internet connectivity with the MBL on it to another network with internet connectivity.
Anyone wishing to use a MBL with mobile devices on a network with no internet connectivity and no computers on - should use the File Browser app and not WD2go. If you made the same initial mistake as me, and you are working with iOS devices, the above procedure should fix the problem.