For clarification, the brake pipes nibbled at by squirrel's would be the front brakes, which are all hydraulic. The handbrake does indeed use cables, but purely to actuate the hydraulic slave cylinder in the rear wheel hub.
Main braking via cables is simply not allowed today. For very good reasons. Cables rust, stick and break. Hydraulics don't go wrong (although their performance deteriorates if not regularly changed) and are thus as close to a "fail safe" system as is possible in mass production. The shame is that manufacturers could easily put braided hoses on their brake pipes but choose not to, to probably save about £50 per car. Shameful.
