Finally, I've figured out the tow cable to my own satisfaction!
In the D-clasp at the front, then through the tow cable bracket at the top of the right-hand tool rack, down past the jack block, then in front of the thing stowed behind that (I'll get back to that in a bit), up in front of the shovel, through the frontmost spare track hanger, then around the second and back forward along the top of the side skirt rail.
I can't
prove that the tow cable was stowed exactly like that when the film of
Cuckoo was shot, but this is the most plausible way as far as I'm concerned, based on what is and isn't visible in those pictures.
I did have to scratchbuild a new front hanger, because during the various attempts to fit the cable, first the top and then the bottom bits of it broke off. That's what you get with small etched parts with folding lines

The fix was to take a bit of leftover fret, drill two 0.55 mm holes near the ends (the ones in the Dragon parts are 0.5 mm) and bend it into shape before sticking it to the model.
I also made the wash basin:
This started as a bucket in the Bronco set of British accessories, from which I sawed off the bottom half. I then made two discs from 0.25 mm plastic card using my oversized punch-and-die set, one for the bottom and a second for the top that stuck out a little along the bucket's rim. Once the glue was dry, I stuck a knife tip through its centre and cut away everything inside the bucket. Then all that remained was to add two handles from bent copper wire.
Here it is on the model, for which I stuck one handle behind the L-shaped pin through the bracket that also holds the tow cable:
I made that pin from 0.45 mm brass rod, just bending it with pliers to the dimensions of the plastic pins you get with the kit. I put a pin like this in just over half of all these brackets, but I still want to add the little chains you get for them in the etched parts.
Then we get to two two remaining items on the right-hand side of the tank, that I had a hard time figuring out, so I took an educated guess and made them things that have approximately the correct dimensions and which seem plausible:
At the back (left) an oil can, at the front a jack block from a Churchill tank. I'm not certain about the oil can, but the film does show that the item here sticks out beyond the side skirt rail, and it also gives me the impression that it may be circular. The can I used is from Tamiya, and at first turned out to be too tall: after I glued it in place, the turret couldn't rotate without sweeping it off the tank. So I sawed it in three pieces to remove a section, but I had taken out too much, which I solved with a piece of 1 mm plastic card that I trimmed to size once the glue had dried. A bit of copper wire ties it to the tank.
The Churchill jack block is because I had first measured the approximate size of this item in images of the real tank, and when digging through spares to find something of around that size, I found this block from an AFV Club Churchill kit. Its dimensions are very similar to whatever was on the real tank, and
Cuckoo did belong to a unit equipped with Churchills — and though I can't think of a reason why they would take this when the Panther's jack block was still present, I think it's plausible enough.