Thanks for all the feedback, I'll wait to see if anything is forthcoming from Pentax.
Keep you posted

Thanks for the feedback, if only I'd known about the issues....
See what comes of the complaint registered with Pentax, not sure why that is is France though. Would have thought UK was a big market for them.

As for a replacement or a refund, feel it would be a lucky outcome from the comments received.

Does anyone know if the new replacement lens is any better?

I would like to commend Pentax on the new camera though, it is a real gem and really enjoying using it, certainly a major upgrade from my trusty old K20.

My 16-50 f2.8 DA*ED AL (IF) SDM zoom has failed after just 6 months, noticed the autofocus was slow and now has failed completely. The motor is possibly to blame, the manual focus overide is fine.
Updated all my kit in April last year from a Pentax K20 and standard range lenses I have used over the last 10 years or so without any problem, updated to the new K3Mk III and bought all new lenses to go with it including 50-135 DA*, 35mm macron 2.8 limited and 1.4x HD rear converter plus flash etc etc. In all spent close on 5K.

Having used ricoh/pentax gear for the last 35 years I am completely disgruntled that a lens of this quality has failed at all. Never had anything fail.
Sent back to retailer who have sent it to the UK repairer John Pye Ltd (Pentax repairers apparently).
Has anyone else suffered the same problem as I have raised a complaint with Pentax (via French subsidary!!).
Repair is not really what I'd want so now we wait and see what occurs.
Repair could take up to 2 months apparently!
I have been a member of the forum many years ago.. good to see it is still active.
Pete