Broken shower advice please

[rocketmanbkk]

Hi

Got called to this shower, custard doesn't know the make.

The top (cold) knob keeps falling off.

The brass part that goes into back is loose & can be pulled out very easy. Pic 4

Any thoughts please?

 

[rocketmanbkk]

Pic 6, sorry, that brass bit though it fits in the back of the shower is loose & pulls out very easily

 

[quality]

Shower doctor.com they are good