The UK can't be the only ones making this type of drone.
With a 15kg payload and considering the size and likely cost of it I would guess most other countries working on such things are waiting for batteries to get better and electric motors to get more efficient and more powerful and for composites to become a bit lighter and cheaper.
Those new batteries the Russians are working on that can be used normally at minus 50 degrees C would be ideal for this sort of thing because I suspect a lot of payload capacity is sacrificed to carry batteries and to keep them warm at 70K ft operational heights so they hold their charge.
Equally those new solar technologies that are spray on would be useful on clear composite materials for the upper wing surfaces to collect power but also reduce weight and probably drag.
Purely an engineering exercise with no intention of becoming a product, a teaser of sorts,
Could say that about all joint German/French projects couldn't you?