knock when pressing brakes

hi there all , I am coming to the end of a five year build of my mk1 golf gti , I have replaced all brake system on my car , now when I move the car out of the garage and press the brake pedal I get a loud knock sound coming from the front of the car any ideas out there?? everything in the car has been replaced for new or restored

Sounds like something is loose to me, is the suspension tight at the top?

Checked everything around the brakes / wishbones / ball joints etc?

Could even be an engine mount