I know the shipping to the UK is a killer but I have to believe that someone on your side of the pond has similar quality spiral tubes. Well made spiral, properly sleeved while pressing will work in most applications.
Any light-weight wood works well for charcoal. Yellow pine is heavy and makes poor charcoal while white pine is light and makes excellent charcoal. I'm not familiar with the trees you have in the UK but I'd think that you could find plenty that would work well. I have Russian Olive on my property but wouldn't think it would be worth trying since it's so dense.
I use the sawdust left from cutting my rocket sticks ( white pine) and it makes charcoal that is nearly as good as my willow. It cooks quicker and the bulk of it is ready to use without having to mill it.
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