Most people vote within the first 72 hours of receiving a postal poll – so says the Trades Hall mob, and they should know.
After that the dog eats it, the jam falls on it, it shuffles to the bottom of the pile etc. Forgotten. After 72 hours.
So ring all yer friends and family who you think would vote YES. Ring them within that first 72 hours and make sure they actually put it in the post box.