This different currency thing is a complete red herring.
I know you're thinking...if the euro looses value you're non-euro currency will hold up....or if the banks go wallop..........
Trouble is that you're exposing your money to the vagaries of the currency market. probably things will swing both in and out of your favour so there's a risk you'll loose if you need your cash at the wrong time.
Just remember that when you withdraw cash it'll be in euro demonination not sterling/dollar.maybe you'll win, who knows!also sterling is quite dependent on the euro. they export mainly to the eurozone so in a way they're linked.
I'm fairly confident that the euro is safe. there's been a lunatic on here withdrawing hard cash out of his account! If he's robbed look at the mess he's in! i believe if the sh1t hits the fan i'd rather have my cash as german currency whatever that may be. so safest bet is having an account with a german bank in germany. i looked into doing this when we'd the last 'scare' before xmas with deutsche bank to be told i'd need 100k...which unfortunately i dont have
so i left my savings here. however there are brokers who can assist you with lesser sums.