Connecting to shower handset??

Hi,

Fitted a recessed twin shower valve and piped up, tested and happy with it. Before sheeting and tiling wall, just trying to figure how I attach the chrome elbow that sits on the wall and connects behind with the service pipe from the valve. This is the elbow that on the shower side connects with the handset flex. Told to use a tap connector from behind by Hudson Reed (shower valve manufacturers), which needs an access hole cut from behind so you can get your hand in and screw it on. Need a mate to hold it on the other side. This sounds nuts! Is there a fitting that secures to the tile, holding a female BSP thread for screwing once tiled from the shower side? or anyone know of an easier way to secure the elbow connector without bursting a hole on the other side?

thanks

would be interested to hear how you did it