I played with an ex-Astra ECU years ago as I had read things (which I can't find now) that said the firmware to run the DBW throttle was on them, as the Astras had cruise (or optional, or the Australian market ones did - there was an Australia member of the forum who was looking).
I got as far as looking through VX hex code and comparing it with a dump from the Astra ECU using MPPS and put it on WinOLS and a hex editor to see where they differed, but never found a routine that looked like a speed holding function.
That's not to say it wasn't there, but I never found it.
Sadly what I had to say at the time is all gone in the recent database flop.
I moved to getting OBD tuner and didn't continue to look, but the the physical hurdle was that you'd need to fit, wire and find where to connect to the ECU the stalk.
Edited by blackoctagon, 28 October 2024 - 04:43 PM.