If he really needs it, B&H does ship internationally.
The last time I looked B&H had a note saying they did not ship to UK.
Shipping from USA takes time, there are import duties on arrival in UK and if paying in $US a card transaction fee perhaps as high as 3 or 4% to £UK.
I do not see the UK listed as a country they won’t ship to. Here’s a screenshot and a link. I’m certainly not saying this is a cheap way to get the camera, but simply one way to get the camera from a reputable dealer who has it in stock.
That is merely the general export restriction, as the US government prohibits certain trade with countries such as North Korea, Iran .... However, Nikon USA has further regulation, as Nikon USA does not want to violate Nikon Europe's territory. I would imagine B&H can ship a Nikon lens cap to the UK, but not Nikon USA camera bodies and lenses. Gray-market items are not under Nikon USA's rules, though.
But as I said, an individual in the US can buy a Z8 from B&H and then turns around and ship that Z8 to the UK privately. Cost is a different issue.