If some of us are having a problem with a colleague, can we approach the Union he belongs to for assistance to speak to the member. We all belong to the same union. If the Manager does anything to this person he is accused of victimisation since the colleague has previously raised a grievance.
That isn't really the place of the union. The union is envisaged to play a role in the relationship between the employer and the employee, not the employee and other employees.
If the employee is consistently problematic, it is possible that they can be dismissed for incapacity due to non-compatibility with the requirements of the job, or due to non-performance.