Thanks for the advice. I successfully soldered an old battery wire between the two switch terminals after removing the switch.
Getting inside the Nevo S70 was simply a matter of removing the two screws inside the battery compartment at the bottom and 'leveraging' off the back of the case starting at the bottom and working up each side (having taken the battery out first). When the case is loose apart from the very top, the case slides downwards to allow it to be removed entirely. Be careful at this last point as there are two wires which run from the circuit board to the small speaker (which is fitted inside the back casing). There is a plastic lug which you can lever out on the circuit board to release the cable running to the speaker.
I found that an old 'kit' of levers and small screwdrivers which I had used to previously replace a broken Apple phone screen were perfect for this job. The screws as mentioned earlier in this thread and not normal ones but 'six sided' ones.