Start with say 100,000 GBP
100,000 - base amount Interest rate - 5% Amount after 1 year - 105,000 GBP Held as EUR 100,000 GBP => 150,000 EUR Interest Rate - 3.5% Amount after 1 year => 155,000 EUR Now, assume two extremes of the exchange rates: 0.6500 as the low and 0.7000 as the high for year end exchange rates: GBP Nominated Acct worth 105,000 GBP EUR Nominated Acct worth 100,750 (low) to 108,500 (High) Note: This is 'without' considering the fees and spreads that you'll need to pay for conversion... So, if the EUR/GBP touches 0.7000 by the year-end, then it is better to convert otherwise deal with GBP only.