Surprisingly for me I actually slept on my last BA Y and QF Y flights, but if there is an option, go for the A380. I found it reclined more than my last very long haul flight on SQ. But if you can't get a seat in Y at the back (will depend on if its old or new config) avoid the middle Y cabin on the lower deck as they seem to start the meal service from the front and rear cabins and this cabin gets served last.