Hemp shiv alternatives?

I'm looking at hemp crete as a building material. The hemp is used as an aggregate with lime. And is good for breathability and insulation. All good stuff.
I don't really want to import materials if I can, so was wondering if there was a similar plant that I could grow onsite. Or whether another shredded plant/wood would do the job. This is for an outbuilding - so happy to experiment.
I frequently have buddleia cuttings, this is quite lightweight, probably airy in structure. Also can get hold of hazel cuttings, and field maple. I'm thinking about whether I have stuff that I could use that is harvested here - general cuttings.
I'd happily grow hemp given the room if a license wasn't required, but I'd probably be hard pushed for room! Would be interested from those in the know if there is another alternative.
I could buy in some hemp shiv, but I'm looking to bulk it out.
It's a bit chicken and egg, hemp seems like such a marvellous building material, but I guess it will take time for it to catch on, and prices to fall, and for it to be grown closer to home.
But if you do know a hemp shiv producers in Sussex, Kent, or Hampshire do tell.
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https://www.fawleyfarmfeeds.co.uk/bedding.htm
Good luck.
It is very widely available in the UK without importing it. You don't say what you're planning to use it for- that's one of the main factors with it and the aggregate (in this case the plant fibres) you use will limit where you can use it without rot or degradation being an issue.
I live in west central Scotland - not where that photo is...