Ace - you're supremely helpful here! The strings are as came with the guitar, they'll be going asap. I play open E, so I'll be going for a light guage - will a light guage help or hinder this issue you think?
Just going back to the tension screw - which one is it exactly? You mean one of the screws on the tail piece? A or B :

Again, these bridges are new to me - basically I feel that the trem arm does not go back exactly to where it started before I whammy... if I can somehow have that lock in place back to the start position, and have no play, I think I'm sorted. No up bend please!