No, we are unlikely to head for the USA anytime soon and apparently they are difficult to offload!.
We looked at picking up some Euros or Pounds as we are heading that way at some stage but I would hate to be holding useless paper if either tanks. Even if they survive, which is highly likely with the pound, the price may drop a bit more. If it was easier to get them without all the associated fees it might be worth it I guess but it seems like a lot of risk. In order to make it worthwhile and minimise the fees you would need to buy quite a bit.
Are you thinking Forex or something like that? I don't trust that electronic money, I say if you can't hold your paper, you don't own it!