Hi Anonymous
Many thanks for the reply.
I had been told that to receive an IP address the APN must be correct and as the Router had been allocated an IP address from vodafone and was showing its connection status as "Connected" the APN cannot have been the problem. Added to that there was only one option shown for monthly SIM cards in the manual APN dropdown list. I assumed this was the same as would be used for the Auto selection. For these reasons I hadn't tried Manual APN.
Prompted by your suggestion (and to be honest, 100% expecting to prove you were wrong:), I tried it out - and lo and behold, it worked!! Data is now passing, pings and web browsers work.
Many thanks indeed for solving the problem.
All the best
Gerard