You'll first need to decide if you want to buy into the S&P500, which is the 500 biggest companies in the US, or an international index fund, of which US companies comprise something like 60+%. Arguably, other markets like Europe have not been doing as well as US lately, but it can be cyclical in the long term. Then you need to decide if you want to go with distributed dividends, or accumulated dividends. The latter means the dividends are automatically reinvested for you. This is very much personal preference. I use Stanchart myself, but I think Saxo is also quite popular. And yes, go with an Ireland-domiciled fund from the London Stock Exchange.