They mostly used players who are children of UK citizens. Lots of players from independent leagues and a handful of minor league prospects and one major leaguer.

Also heard that the British baseball federation operates on an annual budget of $30,000, or something around that, so not all that surprising that it's extremely niche there. That said, qualifying for this and the next WBC comes with at least $600,000 over the next six years so maybe they'll expand at least a little bit