Providing highly trained professional security guards and associated round the clock security services and for over a decade, Prosec UK offer reliable and effective security services. Doncaster and Sheffield,Welcome to ProSec UK Security services in Doncaster and Sheffield. Specialists. A discreet, reliable and effective service. Providing highly trained professional security guards and associated round the clock security services and for over a decade, Prosec UK offer reliable and effective security services. Our 24 hour guarding services operate nationwide at domestic, commercial and industrial premises in addition to local government sites including offices, schools and hospitals