While the K3 might be able to go beyond the limits of many lenses they'll still work OK with it. It's only in pixel peeping that you'll see the limits - I doubt you'll print anything bigger than A3.
The lenses you list are good - perhaps not quite as good as the limiteds or star lenses, but I'm told you'd have seen some of the benefits of them even on the likes of the K20d.
Many people still like the Takumar 55 even though lenses have inproved a lot from when it was made, don't discount old glass it still often gives great results!

One other option not mentioned yet is simply stacking lenses reverse a lens in-front of another (longer) lens. Magnification is the the focal length of the (longer) lens /focal length of the reversed lenses.
Ideally done with a coupling ring but can be done just by holding the reversed lens in place.

If you have more than one lens you can try it for nothing!

Some combinations give vignetting or excessive magnification making it effectively useless, but a 50mm prime with the kit lens (zoomed in) gives ~1:1 simply.

Excellent as always.
My favorite is No 6, followed by No 3 (but that might be partly as my Brother owned a Mustang for years).

All variable ND filters seem to work using crossed polarisers (it would be possible to use a liquid crystal instead but that needs power).
They are known for giving a darker X when used with wide angle lenses (possibly only outside?) which is the only con I've heard about consistently.

How far do you need to reduce your exposures? Rather than a variable ND a ND4, ND8 or perhaps just a CPL might be enough. When using flash you can easily reduce the flash power by adding a diffuser in front of the flash Plain tissue or cigarette papers work well & can be stacked if required for greater effect.

As John mentioned it's the distance from the subject that effects the distortion. With APSC you'll want a wider lens but there's so much ability to crop these days it needn't be a 70mm a 50mm cropped to the same proportions will be fine, as long as you keep the distance about the same.

FWIW I think the original 135mm guideline was partially because 85 or 90mm lenses would have been fairly rare but 135mm were one of the top 3 focal lengths used.

I suspect it's more a matter of the best aperture for the lens. most lenses perform best 1-2 stops from fully open. DOF is certainly not an issue.

Lovely shots Carl.
You certainly got to see the cyclists for longer than we did on the ground.
I took far more shots of support cars than the bikes themselves, which flashed past in around a minute, despite me chosing a spot with a longer view.

Juggling lenses in a Helicopter isn't easy, so having a longer lens with you would have drastically reduced your shots of the overal scene. I found the DA55-300 gave me a useful range and the vibration/windows probably introduce enough distortion that any IQ improvements in better optics become lost.

The scenic views are indeed interesting, so don't worry about including them!

Having to shoot with long telephotos does limit options for backgrounds, your BRDC pavilion shot is way more interesting than just grass. While backgrounds are easier at Oulton & Donnington you managed to fin something even at Silverstone.

I have to admit the historics actually interested me more than the modern single seaters. Here's another one from their static display:

Classic GP by Analyst 1, on Flickr

Great set as always Simon. The shot of Damon Hill is my favorite too.

My own shots from Silverstone aren't a patch on yours but I still think they're among the best I've managed.

Here's one of a Lotus as they were my hosts for the day

Lotus F1 2014 by Analyst 1, on Flickr

And one from the historic parade

Classic GP 6 by Analyst 1, on Flickr

Now I have to work on getting interesting backgrounds, and those celebrity moments...

Glad you're sorted!
Having bayonets between the stages makes it much easier to change the length of extension. The release leavers are also more obvious IMO.