Ideally you want to at least take off the caliper to inspect the pads and clean and lube the sliders. Good excuse to clean the pads and ensure the brake carrier is spotless too. The car will use pad stainless shims/springs. As mentioned, the sensor wire clips onto the inner most pad, the sensor could be detached, or the wiring damaged? I'd use a little ceramic grease on the shoulders of the pads to seat them. As the car is just 3 months old, I assume its Audi Approved? It doesn't matter if you bought it from Ayr Audi, Aberdeen Audi are tied to the same warranty programme, so call them to get them to put it right. Normally the Approved Used warranty is for 1-2 years. To be honest, brake sensor wires shouldn't detach, so I'd want a proper look. When they prep these cars they do the bare minimum.