Some issues in connection, hopefully these notes will help other people.
1. I couldn't see the device in a BT scan. This is because the device only turns on when you actually wear it.
2. Despite having paired the device and apps allowing me to select it, I was not seeing any data in HRM applications.
Applications I tried -
Heart Rate Monitor for Polar
Heart Rate Variability (simple application for testing)
iCardio (Test function only without HRM sensor upgrade)
Eventually I managed to get a HR to display in the iCardio test page by ensuring the strap and pads were wet under the tap, I also wet my skin where the sensor contact will be. It seems that just moistening the pads with a little water is not enough.
3. Once I got a stable signal, I then tried switching to another app (Cardio Training). This failed to see the device until I unpaired it and paired it again.
So now it's working. Using the Cardio Training app during a 40 minute interval workout with the phone 2 metres from me. During this test it dropped signal twice; Once when I went to get water from another room (expected) and again when I went into child's pose to cool down a little. It is stated that the BT signal is not strong enough to get through your body, so again, the latter is also expected.
Update after 10 days use: Working excellently. I do not need to unpair/pair the device from my phone before use each day with the Cardio Training app. Assuming device is already paired, all I do is - Wet strap, wet skin, put on strap, attach sensor, run app on phone - heart rate displayed.