Details of trade mark registrations are publicly available on a searchable database. As a consequence, competitors who may be considering adopting a mark which is the same or similar to yours will be deterred from doing so when they find your registration on the Register of Trade Marks.
A trade mark registration also provides the easiest and most effective means of stopping others from using your trade mark ( or one similar to it ) in relation to goods and services similar to those in which you trade.
You need only show that the competitor is using a mark which is confusingly similar to your registered trade mark.
By comparison, trying to prevent others using your unregistered trade mark involves the expense and difficulty of proving that you have reputation in your mark in the area where the unauthorised use occurred, and that the public is likely to be confused as a result of the unauthorised use of your mark.
Unless your business has a nationwide reputation, registration is the only way to guarantee blanket protection across the whole country.