Try looking at www.eric.org.uk for information about bedwetting. Eric is a charity based in bristol that deals with bedwetting and soiling. Their waterproof bedding is very good. More expensive but worth the money because it lasts.

It is also now not usually advised that you restrict drinks before bedtime. Maybe while he had chicken pox he was not sleeping so deeply and was more aware he needed to go. I also found with my son that additives in some brands of orange squash made him more likely to wet the bed.