The police can also enter your property without a search warrant if, while driving, you fail to stop when a uniformed police officer indicates for you to do so. The thinking behind this is, if you fail to stop your car, it is likely that you have something to hide. Hence the 'need' to enter your property without your consent.
The police can also enter your property after your arrest without a court warrant for certain offences if an Inspector or above believes that evidence pertaining to your arrest may be found at the property (and time is of the essence, ie. if a search is delayed, evidence may be removed / destroyed). In this case the 'warrant' is signed by the Inspector or any of his/her superiors.