Yen/Pound exchange rate

Hi there, not sure if there’s a better place for this question but I was wondering what people thought about the yen/pound exchange rate, especially after Brexit. I might need to get a lot of yen (buying in pounds) at some point in the future. At the moment it’s at 140yen to the pound, which is just below average I’d say. Do you think it might get much worse? Should I lock it in now even though it’s a slightly poor rate? How bad do you think the rate could get? The worst I’ve know it was when it was 115 in 2011 and then it went up to 190 this summer, but with Brexit and everything it couldn’t get down to 115 again could it?

Thanks for any replies!