It's the same here. You can't be booked for being 0.05 BAC on a bike because the offence includes 'motor' vehicle, but I think you can be 'drunk in charge of a vehicle' or something like it. Have never heard of it happening though.
I got our national 'road deaths' data for 2010 yesterday, which sadly included 173 pedestrians, but none of them involved a bike AFAIK (and it's so rare that we do hear about it). I think we are pretty benign.