Well the market for metal detectors is split into military for mine detecting, security for shops and detecting weapons etc at airports and public places, hobby for people looking for metal in the ground as a pass time.
military metal detectors range from mine detectors to the magnetic anomaly detectors fitted to warplanes to detect submarines thousands of feet below under the sea (imagine a hobby detector that good we would all have JCB's)
Security metal detectors include commercial detectors like those used to detect metal lodged within timber, as well as concealed metal objects they use more x-ray type scanners these days.
As far as i am aware none of our domestic manufacturers are involved in the other areas to a massive degree
