I got the numbers from this forum. His source link for the most recent couple of years has annoyingly broken, but the source link up to 2014 works and matches his numbers so I have no real reason to doubt the most recent numbers were accurately portrayed. It matches my anecdotal experience, too. Blu-ray was just never as popular here as DVD, and while DVD is declining faster of the two, I can't see it dropping into second place before physical media dies completely. The lure of the supermarket £5 dvd is too good for the £15-20 Blu-ray on the next shelf over to be a draw.
^ Yep. BR's are wonderful for those who care about the highest of high res and all the features. Most of the people deciding between the two options are more interested in the price tag - and why spend more than you have to for the same thing in a different box?