I am not aware of any specific ranking guideline for qualifying WCs - in practice in recent years they have gone to a combination of players not far off the target ranking for Main Draw WCs and teenagers, plus those via the WC play-off
Great to see Richard enjoying a bit of success. He might not be the most talented British player but he is a nice guy with a good attitude and a solid game. The final should be interesting due to the contrasting styles of these two.