[jasonbvr]

If you went pounds to dollars to yen, you would have lost 1 yen for each pound exchanged today. So if you changed 550 pounds, you would've lost 550 yen which could've bought you a double cheeseburger, fries and a coke from McDonalds. The differences are not really big enough to go through all that trouble. Plus, you're not going to get an exact exchange anyways since the banks always take their cut. So you would actually lose money even if you could gain on the differences in rates.

ATM cards in Japan are smart card versus the magnetic strip which is standard in the US. Smart cards have the gold looking chip embedded in it and I believe are standard pan-Europe so if you have that you should be alright.