I've just been thinking about all this, and wondering if anyone still has boxes for their cubes with the manufacturer printed on - not Slemcka though.
I phoned Slemcka, out of curiosity, the other day and they said that they're not currently supplying their cubes to anyone, but are looking to get them into more shops around November time (so look out for them around christmas!). They also don't have any in stock because they're not supplying to anyone.
I thought that maybe some of the other manufacturers / suppliers could be contacted, to see who they are supplying to at the moment, or even if they would be willing to supply to an individual.
I'm sure if they would only supply a pallet-load at a time then the money could be raised by all the people wanting cubes and then it could be sorted out to get them to everyone - if B&Q can afford to sell them for £9.99 then the trade price couldn't be THAT much, so that would allow for postage costs etc.
Just throwing the idea out there, since I know that my search, at least, has been fruitless.