Solution foundWhat was the solution as it may help others in the future
Power up the unit
Have the unit plugged into the internet socket going to your router
Using the phone plugged into line 1 go into admin mode using ****
Reset the unit to factory defaults using 73738#
Set the unit back to DHCP using 101# and respond with 1
Disconnect the Ethernet cable from both ends
Use the Ethernet socket on the ATA and connect to an Ethernet Socket on a laptop
ipconfig should return that 192.168.15.1 is the ip address of the ATA and your laptop will have an ip address on the same network
Using a browser go to 192.168.15.1
Logon with userid admin and password left blank
Create a password for the admin account and log back in
Allow remote access
Configure your SIP service and save your hard work
Disconnect the Ethernet from both ends
Reconnect the unit using the internet socket on the ATA to a port on your router
After 2 minutes dial up 110# to discover the ip address of the router which should be on the same network as your laptop
Use a browser and enter the discovered ip address
This gets you to the log on screen of the ATA
The logon credentials are admin with the password you just setup
Well that lot worked for me; whether it does for you is another matter!
Make a note of the MAC address of the unit found on the ATA base
This MAC address should appear in the DHCP table of the router or maybe only the ARP table
In all probability the latest firmware will not be installed; if not bring it up to date!
The default Dial Plan is useless and needs replacing; I use Voipfone and they very helpfully had a remote session with me to insert a more appropriate Dial Plan.
At the end of this exercise you should have at least three lights showing on the ATA.
If a Voipfone customer, dialling 155 should return a recorded message saying you have set up your 'phone' correctly.
If the phone you are using has an answering facility then this should be disabled to avoid a conflict with the service provided by Voipfone.
If using the unit's speed dial facility, it takes a while before the ringing tone is heard.
I do not recommend using an ATA at all as it is often best to use a dedicated VoIP enable phone. This could well be a cheaper setup then the total cost of the ATA plus an analogue phone.