There are severe penalties but the courts rarely impose them. Just like someone who drives over another person and kills them probably gets away with £100 fine and told not to do it again. But having jet fighters on standby for the very rare occasion when a lost pilot causes trouble is sheer nonsense. If the infringer is a mircrolight, can a jet fighter fly at 30 knots to "chase" it? C'mon.......
Of course aircraft can be tracked and tracking zone infringers is often successful. However, there are some pilots who know they've made an error and then fly below radar cover to destination!