It's very clear, obvious AND blatant you've not bothered to read the Mi5 website which gives their current assessment of the biggest terrorist threat facing GB today.
Here are the relevant parts:
"Terrorist groups in Syria and Iraq, including Al Qaeda and the Islamic State of Iraq and the Levant (ISIL), possess both the intention and the capability to direct attacks against the West. The UK is a high-priority target for Islamist extremists and they pose a significant threat to our country and to our interests and citizens abroad. Despite the current main focus on terrorism originating from Syria and Iraq, the threat of terrorism also emanates from other parts of the Middle East and regions such as North, East and West Africa, South and South East Asia."
And:
"The majority of terrorist attack plots in this country have been planned by British residents. There are several thousand individuals in the UK who support violent extremism or are engaged in Islamist extremist activity. Some British nationals travel overseas to train with extremist groups and return to the UK with the view to plan attacks, but increasingly the terrorist threat from within the UK emanates from individuals radicalised by individuals and material online. Once radicalised, an individual might decide to conduct an attack in the name of Islam without any prior signs of radicalisation. Simple, self-organised attacks by UK-based Islamist extremists have increased and are inherently harder to detect than more complex and ambitious plots."
Put it this way, it's easier for Mi5 and PSNI to nullify the threat posed by dissident terrorist Republican groups in Northern Ireland than it is to nullify GB based lone wolf terrorist attacks from Islamic terrorists.
Right Wing Terrorism and Left Wing Terrorism aren't the biggest security threats facing the UK as a whole today. They're even easier to nullify than the dissident Republicans in Northern Ireland!
I've explained that the misperception that white people aren't labelled terrorists and brown people are is largely based on the amount of media cover devoted to Islamic terrorism.
The reason for that coverage is because Islamist extremists are the world's most dangerous terrorist organisations today. I listed them on previous pages.
In the 1970s to the 1980s, it was the Provisional Sinn Féin and Provisional IRA who were the world's most dangerous terrorist organisation. We eventually defeated them through various means which is why they accepted the Belfast Agreement which gave them nothing in terms of their own objectives. We achieved our objectives.
You're talking to someone who has lifelong experience in understanding terrorism and counter-terrorism.