But can you legally hunt those worms with dogs

To the OP, I wouldn't worry too much about who sponsors the racing day, hunting and racing go hand in hand back through the mists of time, the formal name for jump racing in the UK is 'National Hunt'. Several races (point-to-point) require the jockey / horse or combo thereof to have hunted a certain number of times in a season with a local or other hunt (simplistic rules, but that is the essence of it). Now, of course, it is legal hunting, with the aim not to be to catch vermin, but more the ride itself.

The Race for Repeal is a race for the Masters of several of the hunts. The politics are secondary to what should be a really fun race by amateurs for whom winning holds far more kudos than it does for your regular race jockey!