Seized brakes front O/S rear N/S

After having the hydraulic fluid renewed on a service I was not happy with brake pedal travel. After 20miles travel the car appeared to lose power. I found that the diagonal callipers had seized on resulting in distruction of the pads and overheating of the discs. It was recovered to the servicing garage who now tell me the master cylinder had failed on one circuit resulting in renewal of this and, all discs and pads and one calliper. At a cost of £805.00. Could the fault have been incorect air bleeding of the braking system