....tyres that is.

Now got 12.5k on my Octy - should I swap the fronts to the back and wear out all 4 at the same time, or wear out the fronts on their own?

Anybody got a favourite?

Your choice entirely. The Owner's Manual recommends switching front to rear if wear on the fronts is significantly greater, but that way you get to buy 4 tyres in one go. It also means going against tyre manufacturers' recommendations that tyres with the most tread should be on the rear for safety reasons.