Sure they matter, but only to the extent that foreign expenditures are a part of your costs.
I.e. sure when you go to the US and have to buy USD with GBP you'l be at a disadvantage, or when you buy some electronics priced in USD, but how big a portion of your spending is that compared to food/rent/commuting/hobbies etc., all of which are priced in your local currency.
I.e. sure when you go to the US and have to buy USD with GBP you'l be at a disadvantage, or when you buy some electronics priced in USD, but how big a portion of your spending is that compared to food/rent/commuting/hobbies etc., all of which are priced in your local currency.