I've had another look at my tyres and discussed it with a work colleague. The front tyre is a little mottled (uniformly throughout the circumference) whereas the rear is smooth. In both cases there is still plenty of tread and no adverse signs of wear.
What we think is that maybe the rear also went through the "mottled" phase and has now worn down further, so indeed the rear is wearing faster than the front as expected. The contact wear area of the rear tyre does look fractionally wider than the wear area on the front - so this also seems to confirm the rear is wearing faster.
I keep both tyres close to their 115 psi so I don't believe tyre pressure is an issue. As for wheelies unfortunately I'm a liitle too old to attempt one
I'll be keeping a closer eye on my tyres from now on.