Rate of positive lightning strikes in the UK

[chrisbell-nottheweatherman]

Following my account of last night's storm (posted in SE&EA regional and Severe Weather threads), it's been suggested that what we experienced may have been a positive CG strike from the anvil of the cell which was just to our west.  However, there seems to be some confusion as to what percentage of lightning strikes are positive.  One member recalled a figure of around 1 per 1,000,000; however, most websites quote "up to 5%" or "around 5%". This paper:

 

http://www.hindawi.com/journals/amete/2015/307424/

 

suggests around 10% of strikes globally are positive, but I wonder if this is higher than the UK percentage due to the influences of US supercells and tropical storms with very tall anvils and a great deal of moisture and heat increasing the rate.

 

I'd be interested to hear any views or inputs on this matter.