It doesn't have to be one or the other. The NAH tool will (I suspect) be massively useful, but that doesn't mean that the UK polo community can't do other things to supplement it.
Here's an idea that anyone can pick up and run with right now. Practice reffing at throw-ins. This could be done on a sole basis, or by buddying up with a more experienced ref. Even if you're not making all the calls that the rules might require, you'll get used to concentrating on the game, calling goals/time etc., managing restarts. All this will build familiarity with the role of a ref, and hence confidence.
It doesn't have to be one or the other. The NAH tool will (I suspect) be massively useful, but that doesn't mean that the UK polo community can't do other things to supplement it.
Here's an idea that anyone can pick up and run with right now. Practice reffing at throw-ins. This could be done on a sole basis, or by buddying up with a more experienced ref. Even if you're not making all the calls that the rules might require, you'll get used to concentrating on the game, calling goals/time etc., managing restarts. All this will build familiarity with the role of a ref, and hence confidence.