Is it my Mira 415 shower at fault?

Water from combi boiler hot to taps but when Mira shower turned on boiler fires up then hot water cuts out after about 30 seconds and shower runs cold. All other functions on boiler are fine and recently serviced by British Gas. Have thoroughly cleaned shower head and have good pressure. Is it the shower at fault in which case what can we do to fix it, is approx 10 years old.