Thanks for the response. I have managed to get it working by following pretty much what you said.
I defined a new IP phone service with type Messages and subscribed my phone to it and when I press the Messages button I get two options on the screen - "Voicemail" which when selected launches the CUC TUI and VoiceView Express.
I did not have to modify the Messages URL on the phone to get this working.
My problems are now how to remove the Voicemail option - it is an Enterprise subscription and then how to subscribe the Extension Mobility User Device Profiles to the new VoiceView Express service as BAT does not support doing this
I guess I should have done a bit more testing before configuring all the users.
I do think that Cisco maybe need to review which IP phone services need to be Enterprise Subscriptions by default. I would like to see Voicemail and Personal Directory modified so they are not Enterprise subscriptions out of the box.