Your retirement money should be in the currency of the country you are planning to retire to, given the high risk of currency movements going the wrong way in the run up to retirement or during retirement (eg. see the problems of UK pensioners in Spain).
One way to put money into a currency is to buy property in that country. Are you planning to retire to the UK? If you are going to buy property in the UK you should know that stamp duty increases have made transaction costs pretty high now. I would recommend only buying if it's a good rental that you are going to hang on to for a long time, and recognising that this is probably an uncertain time to buy a rental, given that it is about to become a lot more difficult to evict tenants and that the Labour party are talking about rent controls. The other way to buy would be to buy the property that is going to be your long-term retirement home, but depending on how long it is until you retire you risk it not being a good rental in the meantime and effectively losing money as against other forms of investment. So I would say only do that if you have you heart set on a particular property or kind of property that is available now and may not be available again in your lifetime, recognising that it is a heart purchase rather than a head purchase.