Many thanks for the suggestions but to no avail. Perusal again of the manual again provides no clarification, and the manufacturer has not yet replied to my email enquiry. I withdrew the battery which tested at 2.9V which should be Ok, however I will replace with a new one today. In addition the "Quick Start Guide" describes how to access the different functions but no direction on how to access the NORM (surface). This is frustrating. I had a bad feeling about this when I opened the black plastic storage box for the first time and one of the two catches broke off - I hope I haven't bought a duffer.
On the bright side, the weather is great and the water clean and 20 DegC so getting wet tomorrow with my Suunto Stinger, which has been incident free since purchased 18 months ago - Aeris please note!