I assume you have some programming knowledge, so have not included everything, but....

To have calls direct immediately to voicemail, and show on all phones, you need to set the group divert to VM.

On any phone in the group (all phones by default are in group 1, 180), scroll down to GROUP DIVERT, and use the menu to select the group and select DIVERT TO VM.

The option will only be available in the menu if you have setup a group mailbox.

To setup a VM box for a group, you need to go to system programming > Extensions > VM boxes >Standard boxes.  Select group 180.

You can use short codes, or set the short code to a feature button to allow you to turn on/off easily.

For example:

792 Group Divert All Calls
793 Group Divert On Busy
794 Group Divert On No Answer

So, 792180710 would divert all calls for group 180 to VM.  180 is the group, 710 is the 'extension' of the VM mail box.

Hi Lectrician , I,m afraid I jumped the gun .
The above only works when using grp divert all calls .
so, 792180710 will light all v8 term LEDs. ,but 794180710 will not and this is what my customer requires . I,ve been over it time and time again as per you advise , but no joy . Once again ,I would appreciate any help with this .
Thanks

Hi Lectrician/ i have it now . I was still putting ' system voice mailbox ' on. Working ok now .  I notice that 'grp divert all calls' puts a message on the screen ' grp divert set' , but 'grp divert no answ' doesn't change the screen at all .
However , I now have the top led showing at all xtns  indicating a message and 'new grp message ' on screen so ,thanks again .