How far away are we from Blackpool?

I was impressed that you could see the Lakeland fells so clearly from Blackpool. I used the usual trick. My little finger is worth 1 degree. The fells subtend half a degree. Half a degree is 8.7 x 10^3 radians. Arc length = radius x angle in radians. The height of the fells is the arc length. The height of the fells is roughly 800m. So distance to the fells is 800/8.7 x 10^3 = 92km. That's far too big!