My last pair of Blundstone 500s got a hole on the left foot round about where the big toe would be. The leather stretched and parted from the sole unit. I've never had that happen before so I wrote to Downunder boots and they are talking to Blundstone.
In the mean time I didn't want to be bootless so I bought a new pair from Shoeland.co.uk, only this time I bought the 550s and in a half size which is wider but not longer. Sixteen hour delivery too!
The leather liner make a real difference and the leather seems slightly thicker. They do seem to be more comfortable than the 500s. the wider fitting rocks too. And the best bit, they are the same price.
Just a Blunnie fan and no affiliation with shoeland or Blundstone.
I did wonder about going for the leather lined version, may still consider that after what you have said.
Graham