you will get a notice after a couple of weeks that if you don't pay or set up a court date a conviction will be entered because you didn't dispute the charge
If you don't pay your ticket by the due date, you will usually be given a notice by the baliff that warns you of the consequences of not paying your ticket and an extension on the due date. You can obtain an extension beforehand if you provide a reasonable excuse to the baliff. If you cannot pay your ticket at all or refuse to pay, the magistrate can summons you to court where he will decide what to do next. Often the baliff will be ordered to seize property amounting to the value of the amount owed, or a brief stint in jail is common as well.
You can always challenge a traffic ticket in court, as is your right.