My answer was assuming it was major currencies.
I see an edit that you put up that changes things a tad, but the basic principle is still there.
But not losing money on currency fluctuations is handled with the futures market.
A businessman could dial in a million dollars at the desired exchange rate using 100:1 leverage (or even more maybe in the UK).
For the small price of 10,000 pounds, he could guarantee his price for 1,000,000 when he needed it. Futures go quarterly, (at least in the US) so if he needed his money in September, and the rates were good right now, he would be in the market already with a September expiration, at which point, the other 990,000 sterling would come due, and his currency of choice would show up on his doorstep.
Getting to something like the yuan might require a double transaction, because I don’t think there is a direct exchange of sterling to yuan right now. You would likely have to get USD, then head to the yuan, so you might have to double up on the process. That might get a little tricky, but I don’t think it would be too bad.
The thing about futures is, if you got them early enough, and price moved in your favor even more, you could make money on the money, while you were waiting on the final transaction.
So, say you needed a contract for September and you had rates that favored you right now. You made the purchase, then, the sterling jumps up greatly against the dollar. You would sell your current batch for a profit, and then rebuy the cheaper dollar for the transaction later, and bank the profit for Mr Businessman. If it moved against you, and the pound dropped against the buck, no harm, no foul. You’re already ahead of the game.