The IRA were bombing Britain all the time. There are still no trash cans in the London subway system today; they were taken out because the IRA might leave bombs in them.
The IRA even hit Downing Street and one of Thathcer's political conferences.
There might have been stepped up security in Northern Ireland itself, but security in London during that period was far less than during this stupid "War on Terror", and there weren't all these stupid "anti-terror" laws. The regular police didn't even carry guns back then.
Thatcher tried to use a regulation banning the voices of Sinn Fein from being put on air because they were advocating terror. The BBC just played the footage and used voice-over artists to say their words.
And this was how 80's Britain responded to the IRA, which was a large and well funded organization.
So I have an existence proof that you don't have to turn into a police state as a response to terrorism, because I grew up in a country that chose another option.