Pentax/Sigma - lens nightmare

Hi All,
haven't posted for ages or been to the site - hope everyone is well?
I love my K10 - it is such a well designed tool.

Have you ever heard the conundrum about the fox, the hen and the grain of seed at a river crossing - well my nightmare is akin.

Here is my problem and would welcome advice.
Bought a Sigma 18-50mm (old type) and it wasn't sharp on the camera. So I jiggled with the focus adjustment and it looked like it was better.
Turns out the lens was faulty - so the lovely customer service people at Sigma fixed it calibrating it to my body and now it is really nice.
Bought a Sigma 10-20 this wasn't sharp? Sent it back; was sent a new one. It was a little better but still not sharp!!!
So i obviously need to send body and camera to Sigma for calibration.

I have noticed now that my Pentax 80-320 (previously reliable) is unsharp.

When I jiggled with my K10 focus programming I put it back to setting one. Is this the zero?

So what do I do? Is any one following this epic?

Do I send the camera and Pentax 80-320 back to Pentax to get it serviced. Then send the camera and Sigmas to Sigma for calibration!!! Because Pentax may adjust my camera.

What happens when i buy a new lens. Do i send it off again? It cost postage (£25) and the service charge!!

Meanwhile i do the odd paying job and would be losing out.

My head hurts... what really bothers me, (is in my experience) Pentax have the worst customer service until you get to a manager of any company including MFI!!!

The last time I sent my istD* they "lost" it for 3 months and then sent me a body with a dirty screen.

Does anyone have a magic wand?

You don't have your location specified, so we don't know where you are, but that's easy to fix. So I would suggest this:

Find someone with a K10D who is confident that their body and lenses are focusing properly (preferably someone that's actually confirmed it with the focus test chart).

Meet up with them, and adjust your camera to a couple of their lenses.

Then you'll be confident that your camera is correct, and you'll be in a position to evaluate your lenses.

Finally, buy the person who's helped you several beers, or alternate preferred tipple.