I bought my co-worker's leftover British Sterling cash from him because he didn't have time to change it on the way back to the US. You can always see if anyone you know is going to that same country in a few months and sell it to them. I got 32 pounds without having to pay any transaction fee and we used the exchange rate that was given on the day he withdrew the money from an ATM in the UK. Yes, it is well in advance of my trip, but I may be able to use it at Heathrow towards my initial transit purchases; I won't have to wait in line at an ATM at the airport.