The thought did occur to me! However I want to actually be able to live with the thing...plus have you seen how much "retro" or "vintage" materials go for these days? I'd wind up spending an appreciable portion of the value of the car for a couple of metres of carpet...
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This morning I went out and grabbed a new pot of wax to replace the one buried somewhere in the back of the garage, then got to work.
I'm not a professional automotive detailer, but I think this has come out looking reasonably presentable.
In addition to the obvious polish and wax action, the glass has all been cleaned inside and out and the outside of all the windows (but NOT the windscreen) have been treated with Rain-Ex. I don't like this on windscreens as it has without exception just resulted in wipers that smear and judder so I keep it well clear. It's great for the other glass and mirrors though. It's only a theory, but I reckon that the way it makes water just bead and run off helps keep the windows cleaner for longer as well. I've never actually conducted any proper tests to see if that's true or not.
Hoping that if my schedule co-operates tomorrow I'll get her dropped back off with her owner. If not (and it's looking like it will be quite a hectic day) that will be pushed back to Tuesday, and I'll take the opportunity to apply an extra coat of wax.