When it comes to the police numbers, terrorism should be a minor part of the argument. While it is current (and not to take anything away from any of the victims or their family's) the bigger issue in regards to police numbers should be the national murder rate (which sits at 500+ yearly and is on the rise), rape and domestic violence figures.
Yes terrorism is a problem that needs to be dealt with, but stopping it is going to require better intelligence, data gathering and data analysis, not having more police on the streets.
What will lower the crime stats is having more police on the streets who are able to respond to the crimes taking place every day in the U.K
Stopping terrorism should be a minor point in the argument of police numbers, not the whole argument.