Hello mate, great to see the resurrection of your project, looking forward to the updates shortly. Office work. Phnar.
The eGas throttle pot I'm using is very similar to the one you posted a pic of, albeit mine has a metal rotating cable holder and has the cable fixed onto the rotator, presenting an eyelet for mounting onto the pivot assembly. Mine's out of an Audi S8 (and I presume A8)....if getting a second user one, then dont get it confused with the cruise control unit - they look identical. Ask me how I know. Somehow mine got switched somewhere between me buying it and handing it over to MBE for callibration (to the ECU) and then mounting it on the engine. It cause a few moments of head scratching when on the dyno, when we couldn't control the throttle!
The newer unit I have no experience of; I did also investigate the integrated pots that form part of the throttle pedal (a BMW one in my case), but they're bloody odd looking things to retrofit into our cars, not at all in-keeping so I binned that idea.
The Penny & Giles ones are interesting; I used to use a P&G position sensor on my Westfield (not an eGas one though), on the 2.0 XE Red Top engine. Steve @ SBD was a big fan of them, as you say, motorsport quality and small. If you want to pursue this option, let me know, as I'm sure Simon my wiring guy will know where to get them; if needed I can get one locally and ship it over to you.