That's not British CX, that's any country other than Belgium and Netherlands.
Who is following Orts, Kuhn, Boros, Strohmeyer or Konwa? Where is French, Italian or German CX at all* ?
The second GB rider (Mein) is higher UCI ranked than the second from any country other than Belgium and Netherlands, but if he were Belgian/Dutch with the same results, he would be ranked 11th/6th nationally.
There is maybe a bit more strength in depth in the women's ranks, but the best second highest of any nation other than Dutch is Brouwers, but she has 8 Dutch above her.
* in elites, plenty of younger riders
(positions from First Cycling reporting of UCI standings)