Agree with you completely here. I'm a season-ticketer with GUFC (happy tonight) :D and I know a fair few of the fans would also have Connaught Rugby season tickets. Really frustrating that both home games are on Friday evenings. Attend the odd GAA match, though not as often as when I was a kid.
On the OP, I used to work in HMV in Kingston, Surrey and a local teenager came in one day wearing a GUFC t-shirt. Went up talking to him but he didn't know who they were. He had been given it by "some Irish relatives".