If it was not for the space issue, and because you can obviously afford it, then the Drake would be a no-brainer.
But to save a few quid and with your space issue, the Cadet 3 Eudmin does appear tempting, I agree especially if you are fitting it yourself.
No worries with your flange. Mine is getting like that, and while this will be your last toilet on that, it should work fine. The wax ring will take up any slack. Although you will need to do something with those two other bolts.
Instead of using a long supply line, having looked at your set up I would solder an extra piece of copper down the wall; then solder a bronze 90 on to the pipe at the bottom with threads on the other side; then screw a short brass nipple into that (with teflon); and, then screw on to the nipple a new ball valve angle stop (with teflon). To all of which you would attach an ordinary 1 foot supply line. And I would secure the pipe to the wall using copper bell hangers. It would look neater and you would thank me later.
I am struggling to get over the shower head faucet and bucket sink but with what you have you could easily plumb a vanity in there if you are willing to extend those copper pipes down the wall by soldering them.
As an aside, I am a little worried that all of this strange plumbing in your picture looks so recent. A little extra effort and a few more bucks earlier on would have brought much better results.
At the moment a Toto might be too glamorous for this bathroom even if you did get it to fit.
Cadet 3s are less image conscious. They just get on with the job. American standard really.