For those who might be interested the Big Apples look like they available for the Birdy wheel size, think there are issues of fitting them on (fouling the derailer in low gears). If anyone trys them I would be keen to hear their experiences.
I contacted Schwalbe about these tyres (355/50) a few weeks back, and they never got back to me. I will try again, as they are not readily available in the UK. Not sure about clearances on the Birdy, but it may well be tight.
Personally, I would not fit them to my Birdy as their bump-absorbing properties are not as crucial on a fully-suspended folding bike. They are also heavy. However, some people swear by them.