Unless you're VAT registered like a sensible person.
Be careful with the VAT in the UK, it's not as straightforward as just registering and claiming it back/not paying it and if you get it wrong the penalties are not pleasant.
To claim VAT back on outputs you need to be charging VAT on the inputs you can't just use one side.
So because the sale of bitcoins doesn't attact VAT then you are unable to claim it back on the purchase of the machine.
If you buy hardware to resell then you can claim the VAT back as you would charge it on the sale.
This was the advice given to me by my accountants after discussion with HMRC.
Not saying it's 100% correct as this is new territory but something to be wary of.