G'day Mike,
I was going to answer you off line, but the last response to your question prompted me to reply here.
The AIF and AFC had sporting teams. I would then assume that the RNAS and other British services followed suit..
The AFC training squadrons based at Leighterton, had teams ranging from tug o' war to rugby.
They even played a local team in cricket and then as now the Aussies beat the Poms

. Don't steal my thunder and mention the rugby.
As for your particular RNAS chap. My guess is that he played before the war.
In Australia before the outbreak of the war, Polo was quite a big thing, in fact Dacre Stoker who became skipper of the AE2, transferred from the Royal Navy to the RAN as he had heard of a wealthy Aussie businessman looking to pay polo players.
As for this particular RNAS chap, he came from a noted rural family, my guess is that he played on a regular basis. I have not heard of a Polo league, but the AIF did run horse racing carnivals etc, so Polo is not out of the question.
BTW what are you doing watching "Pretty Woman" ?
Andrew.