Sorry, but my major question is why (for a couple of hives) you would even consider an impellor-type mixer?
While I would suppose that it might give more thorough (thus quicker) mixing, I also think that would only apply to large batches. For a small batch, my expectation (experience anyone?) would be that they would be an air-entrainment liability.
The second problem that I would forsee would be that, in order to minimise air entrainment, the motor would have to be started with the impellor fully submerged It would have to be started against a considerable resistance. Which is precisely how one would burn out a conventional drill. And hence, an impellor-type attachment would demand a more expensive drill.
On the other hand, the corkscrew type, while admittedly giving less vigorous mixing, is therefore going to require less torque to drive it, going to entrain very little air and can be started with little or none of the screw below the surface -- so it can be started under little or no load, which should be, allround a much better match for a conventional (cheap) drill.
The slower (gentler) mixing of small batches is hardly a disadvantage for the domestic "2-hive" hobbyist.
Expressed another way, even if Thorne's £70 impellor cost the same £20 as the corkscrew, my expectation is that the corkscrew would still be the better choice for thee and me.
Why do you think the impellor is better for you?
And having also bought a variety of stuff from abroad, while airmailed small jiffybags can be astonishingly cheap, even the weight of a book costs a lot. The packed weight of a yard-long stainless shaft is going to make it either expensive, or very very slow!
I tend to discount the cost of delivery from T's because rather than buying individual bits, I generally 'batch up' an order, sometimes with friends, to get to the £100. All too easily done!
