Small concrete pier foundations – how do you normally form and level them?

[PileLabProject]

Point missed. There's no issue with cardboard tubes - they're cheap, strong, biodegradable, plastic-free and are already available. All advantages over your system.

Take what exists and improve on it, rather than starting with something else that's inferior in every way.

I understand your point.
I’m not trying to prove at this stage that the sleeve is better than cardboard in every respect. The reason I’m exploring it is that it allows the shaft and enlarged base to be formed as one continuous stay-in-place element, while the support controls height and position.
Whether that overall system offers enough practical advantage over a cardboard tube is exactly what the prototype tests need to answer. If it doesn’t, then that’s useful information too.

 

[PileLabProject]

This could be a game changer for the millions of UK diyers struggling to cast and level reinforced concrete piers when building their garden sheds.

Fair enough — it’s definitely a niche problem, not something every DIYer will ever need.
I’m not assuming a mass market at this stage. I’m just trying to find out whether the people who do need this kind of foundation would find a simpler system useful. That’s what the testing and feedback are for.