Redfield.....
You can have 2 handling agents working in tandem with each other. Take Windsheer's base at Cardiff. There are two handling agents there. Servisair run front of house and all ramp operations (as Airway Handling) whilst Aviance only provide front of house and grooming services. Same works with BA at Bristol. Servisair provide ramp services whilst they provide their own front of house staff.