You can buy Vanguard ETFs or any other ETFs through any stockbroker, either online or traditional. Vanguard has ETFs listed on many exchanges - US, London etc. You can buy on any of the exchanges through your broking a/c so there's no real relevance to your point about Vanguard opening in Ireland?
The biggest and oldest platform is the stock market itself. Just open an online stockbroking account and you can buy any ETF you want through that. Fund platforms that offer exposure to non-listed (non quoted) funds are far more cumbersome and probably more expensive although I don't have any facts to hand to say that with certainty.