Choochoo-baloo I don't really understand why you're worried. As you've got a surface plate you can check whatever V-blocks you buy. IF they're not to specification and you bought them from a reputable UK supplier you can send them back.
Jumping to conclusions about the quality of a product depending on where in the world it was made is illogical. If you read industrial history you will find that assumptions of quality based on Nationality always been dubious. Birmingham was once infamous for churning out cheap nasty tat even though many seriously good firms were also located there. Nowadays it's even more difficult to generalise. Manufacturing and services are much more globalised. Design, manufacture, sales, tax, management, ownership etc. can all be based in different countries. What's manufactured by anybody will be aimed at a market: as Ketan remarks this has space for the good, the bad and the ugly.
Rather than worrying about country of origin, you're better off buying by specification and checking it. As this is liable to be costly and time consuming, buying by reputation is quicker, though you always need to confirm that a reputation is still justified. A brand-name is nowhere near as solid as a reputation: when a company goes out of business their brand-names are usually sold to the highest bidder. I always treat brand-names with suspicion.
My V-Blocks are fine for what I use them for. I've no idea where they were made.
One thing about the methodology used in the 'crap' video worried me. The diameter of the dowel is small in comparison with the size of the V block. The chap may have been measuring the accuracy of the notch at the bottom rather than the accuracy of the V surfaces. I wish he'd used something bigger: Jason's test with the shank of an HSS cutter is much more convincing.
I'm quite intrigued to know what will be made in the Choochoo-balloo workshop. Not a criticism, but chaps new to metalwork don't normally start at the precision end of the hobby: it's expensive. If the plan is to own 'quality' tools for pleasure rather than profit, that's fine by me.
Dave