Nobody on either side (apart from the lunatic fringe) wants to back to the days pre-ceasefire.

People on all sides recognise that even if they play the populist card in elections.

Even if the nationalists become a majority in Northern Ireland I don't personally believe that there will be a united Ireland. Even in the unlikely event that Britain abandons Ulster I can see an independent Northern Irish state before there is ever a united Irish republic.

You may be right but, does N.Ireland have sufficient levels of manufacturing or other industries that would could sustain the North as an independent state.
Also, to overcome the problems which Brexit will bring, they may wish to be part of The EU and this would raise further interesting questions about their constitution and whether they would want to align themselves to Westminster or Dublin.

I there the appetite in the South for a United Ireland? The troubles stretched the resources of the British army, could Dublin deal with the UVF/UFF acting as an IRA in reverse? The loyalist population in the north would never accept a united Ireland without a fight.

Well with the NHS in crisis, society more divided along ethnic/socio-economic lines,a harridan in No 10 and Bananarama touring lets give it a go for old times sake.