The Birmingham pub bombings (for example) happened in 1974. The Belfast agreement (ending the troubles so far) was signed in 1998.
>requires very strong support from a very sizeable minority (e.g South Africa, Northern Ireland)
Please see https://en.wikipedia.org/wiki/Demography_of_Northern_Ireland.
You will note that Northern Ireland has a plurality of Protestants (48%) compared to a sizable Catholic community (45%). The majority of people in Northern Ireland do not support a united Ireland up to this point. At some point in the future that may change and a referendum for reunification may be held (if the Irish government agrees). And, note, it is not at all for sure that the Irish government would agree because Northern Ireland is a cats cradle of trouble and problem - demographically, economically, politically and in terms of civil order. I think only with very significant backing from the EU could Ireland contemplate taking it on.
Currently the UK (read England, because the Welsh and Scots are also net recipients of significant monies from England) subsidizes every subject in Northern Ireland to the tune of $7k per year, if that is "crapping all over Ireland" frankly I'd like a bag of that shit please.
And frankly there is peace in Ireland now because the IRA lost, it lost support in it's communities and it lost interest in freedom fighting because one element of it realized that a political solution had been available for at least 10 years, and one element realised it was far more interested in trading drugs and protection.
Anyway : please do some research and reading and don't use straight falsehoods to support an otherwise reasonable argument. Perhaps traveling to Ireland would be a good start.
NA had two minorities with opposite enough ideologies that they got violent. The UK would have never succeeded in keeping the peace there were it not for having a good chunk of the population on "their side". The violence eventually came to mostly an end because the IRA blew up enough crap that the British were willing to mostly throw them a bone in the Good Friday agreement and everyone was sick enough of the fighting to reach an agreement. The agreement was satisfactory enough for enough people that most combatants laid down their arms. An agreement so favorable (i.e. favorable enough to get them to stop fighting) to the republican faction(s) would never have been reached without the violence spilling over into England to a greater extent in the 1980s and making people ask tough questions like "why does what they do even matter to us?". You can call that a "loss" or a "win" or a "pivot to drug trafficking" or whatever you want to make it compatible with your politics. The framing doesn't really change what happened. Considering your characterization of North Ireland I don't expect you to frame the issue in a neutral way.
Consider how the troubles might have played out without loyalist factions. Starts looking a lot like some other, nastier, more resource sucking conflicts. Local support is required any time you want to make a bunch of people do stuff you don't want them to.
But, the loyalist factions were the majority, post WW2 it's just for sure that the UK wouldn't have (and certainly wouldn't now) hang around in Northern Ireland, apart from most of the people in Northern Ireland historically wanted to stay as part of the UK. A minority wanted to leave and fought a violent campaign to do so. The minority was ruthlessly discriminated against and terrorized by the majority - which complicated matters to say the least. These issues do not boil down in the way that you indicate, things are complicated. An agreement like the Belfast agreement had been on the table for the IRA for many years - and frankly it's not very favorable, the only major concession that I can think of was the dissolution of the RUC - but is the police service of northern ireland really that different? I mean it is vs the RUC of 1975 (that's for sure) but vs the RUC of 1998? The big issue that the IRA's final spurt of bombing decided was that they didn't disarm before the agreement was negotiated and signed - but instead after it was agreed and signed. The two truck bombs were painful, but Manchester would not be the city it is now without the last one - and docklands doesn't seem to have suffered much tbh. The Bishop's gate bomb in 1993 was probably more economically impactful than either, and there was no hint of compromise after that.
The UK has very limited economic, military or geographic interest in Northern Ireland. The oil was elsewhere, there is fishing - but we are talking $10M's per year at the most there, and most of that goes to NI boats in any case. There's no reason for the UK to be there apart from the fact that a) the bulk of the population think that they are part of the UK and b) the irish government would be in the mire trying to deal with it if it suddenly came to be their job. Without these two factors there wouldn't have been a conflict, because the UK would have dropped it like a hot coal.
The "but they have tanks and nukes" argument has been long debunked. To actually run an oppressive nation you need boots on the ground which requires very strong support from a very sizeable minority (e.g South Africa, Northern Ireland). The less firepower the peasants have the smaller the minority you need is. You can't fight a insurgency with tanks and bombs without destroying the things you seek to protect. If you're England crapping all over Ireland or if you're the US crapping all over Iraq you can kind of make it work as long as you have political will and keep the death tolls low because your supply lines and political support are isolated from the violence (notice how quickly the Troubles wrapped up once the bombs started going off in England). It's much harder to fight an insurgency when people are sabotaging your supply chains. See the 4chan copypasta someone else posted for other details.