Sorry typo meant to type 0.01 gbp/kWh was a bit baked.
So yah think it’s ok to buy used miners? Should I ask any specific questions to the vendors so I determine if I should buy them or niet?
That is more like it. Unfortunately, you've probably picked the absolute worst time to start. There's a shortage of new gear, and with the rise in price and not much new gear coming online the profitability has gone up a lot and looks like it will stay that way until the miner manufacturers start delivering more or the price goes down. Eventually, the manufactures will manage to get some fab capacity and will dump as many miners as they possibly can, which will reset profitability again.
But right now, people see the price going up, and profitability really high, and are paying prices for gear based on thinking the price is going to go even higher.
With your power cost you could be profitable with an S9 even if the difficulty doubled. And even though the price of used S9s have nearly 10Xed in the last 6 months, (I think they are up to $250 per miner with psu), you'd be able to make back your investment in 3 months if conditions remain the same.
So I'd look at S9s or Avalon miners in the 60 to 80 W/TH range. Maybe
Canaan Avalon 1066 would work, those you can still buy new, and they have a reputation for being higher quality. With power that cheap I don't think it makes sense to pay a premium for super-efficient gear.