How many Brits have bluetooth turned on for marketing?

A question from reader, Hardeep, on the subject of bluetooth marketing:

I was wondering if you have any idea of how many brits have bluetooth enabled phones with bluetooth actually turned on?? with regards to the effectiveness of bluetooth for marketing. Me myself only switch it on when I’m going send or receive something, and then turn it off again, I wonder is this is what most people do?

Any thoughts on this? I’m going to see if the chaps at Bluepod have a perspective.