Also, it’s not entirely clear to me that each of the spun-off orgs need to have the whole cumbersome dual US/UK structure. There are simpler ways for a UK non-profit to be able to access tax-advantaged donations from the US (e.g., a so-called “Friends Of” organization). And as you imply, UK charitable regulation is more onerous, so it’s not clear that an organization whose funding and operations were primarily in the US would find having a legal existence in the UK sufficiently worthwhile.
Also, it’s not entirely clear to me that each of the spun-off orgs need to have the whole cumbersome dual US/UK structure. There are simpler ways for a UK non-profit to be able to access tax-advantaged donations from the US (e.g., a so-called “Friends Of” organization). And as you imply, UK charitable regulation is more onerous, so it’s not clear that an organization whose funding and operations were primarily in the US would find having a legal existence in the UK sufficiently worthwhile.