Two questions - have you ever pruned them and if so,when, and if you haven't pruned, are they close to trees?

Thanks for that Bamboo,i have only dead headed and lightly pruned in spring.They are nowhere near trees and the funny thing is i have 2 lace ones in my front garden that are flowering well?

Hmm, that is odd then - quite often, if they're in a dryish spot in the garden (near trees or large shrubs usually) or too close to a wall where its dry, then they refuse to flower. They don't really need ericaceous feed though, that's reserved usually for blue hydrangeas in fairly alkaline conditions. If dryness isn't the problem, I can only suggest a top dressing of sulphate of potash around them in early Spring, just before, or as, growth begins.