It's a bizzarre thing... I, just the same as OP, get another website start to load and then it lands me on AppStore on either William hill or ladbrokes app pages. I Don't gamble whatsoever so view this kind of advertising as an invasion of privacy and overstepping the mark. I find it worse than...
I get the exact same thing happening on my iphone6 too.
The worst occasion was when it did it 4 tIkea on the trot within a couple seconds of me resetting nsc .
It always seems to take me to gambling app purchase pages.
Most irritating...