I would say that, if it's legal to sell them to anyone, it is the correct thing to do (even though I agree that they are free to impose any restrictions they may wish). In my opinion, retailers and wholesalers should not, and should not be expected to, unilaterally restrict sales on the basis of their opinion as to the ability of the purchaser to use the product correctly and safely.
Well it's an opinion. TBH I don't have too much of a problem with it, lets face it, there have been occasions in this forum where we (collectively) have done our best to dissuade some people from doing work that we can see is likely to be beyond their ability to do safely. And I can see why a wholesaler of CUs might not want to be "part of the problem". But I don't think it's that much of a hurdle (see below), unlike some other wholesalers I've come across in a different field.
There is another reason for being "trade only" which makes perfect sense. Once you sell just one item to a consumer, then a whole raft of consumer orientated legislation comes into play - not just in terms of warranties, but in terms of having to pay into things like recycling schemes. It's why my employer is "business only" for hardware sales - we'll sell to anyone as long as they can make themselves look like a business (eg sole partnership).
From what you 'know' of me, would you think it 'reasonable' and appropriate that a company should refuse to sell me a CU?
No, and furthermore, I very much doubt that he would. At this point, I'll disclose that I've been in touch asking about this, enclosed details of my qualifications and some photos of my work, and he's accepted that on the basis of those he's happy to sell to me.
Now, apart from it clearly being a small outfit who's having his own badge put on products from China, what are the objections (technical) to the stuff he sells ? Several have hinted that there are problems, but no-one has actually said what they are other than inferences based on it being a small outfit. There is a lengthy thread (or threads) on other forums, and I don't see any problems being raised in them.
As I see it, he's got a nice product (compact RCBO the size of a normal MCB) at a good price - so where's the catch ?