^if the shoe digs into your toe the shoe is too small! You definitely can't go DOWN in size. Heel slippage is usually about ones instep being low. Not about the shoe being too big. Buy a pair on tongue pads to fix the problem:
That creasing is normal and occurs on all shoes. Of course leather creases from where it is bent. There's no leather in the world that wouldn't crease when bent.
On Olfe you definitely can't go down in size. The Olfe is smaller in width than the Hiro. Either stay at 6.5 or take a 7. Personally it sounds like your problem is with a low instep and wearing shoes that are too small so I'd take a 7. An increase of 0.5 in length doesn't really create any more problems because it only adds approx 1 cm to the total length of the shoe i.e more toe space.
Thanks, I'll stay with 6.5UK for the olfe last. I think I'll size down on hiro last for future purchases for a slightly snugger fit. I actually have a high instep, I can fit into a 6UK but with a semi-big V lacing. Was about to iron the shoes to try it un-crease it and re-crease it the way I want, so that it would not press onto my big toe near the knuckle area for the right shoe, but now it seems pretty comfortable while walking with no discomfort.