So I am currently shopping for a 18-19 Reg Range Rover, being Republic of Ireland we only have 2 to choose from really and that is the 2.0 PHEV or the 3.0 Diesel.

No the wife is coming from a Tesla Model S and loves electric, so I am leaning towards the PHEV. However they do have a reputation of being problematic, seems to be from early owners however and software problems (so assume should all be cleared now). The road tax saving will be considerable also over here, as road tax for the PHEV is €170 compared to €750-€1,200 for the diesel versions.
The diesel would not be an issue for me as I'm a farmer so could then use it personally then also to pull the trailers and use in the fields, but in reality this will be the wife's main car to carry the kids around and for the long journeys to West of Ireland that are regular.

Anyone have any nightmare stories on the PHEV or the Diesel? What should I be keeping an eye out for? What are current owners feelings and are they happy with their RR?

I love my SDV8 4.4 diesel along with dpf fuel dilution and all lol. = several oil changes per year.
I avoided the V6 due to all the stories about crank failures etc
I dont believe your wife will love the very short range the Phev gives you

If I changed today it would be petrol 5.0 but the love affair is far from over  2018 SE SDV8 4.4 Byron Blue

3.0 diesel is a great engine and very smooth. I've had 5 cars with the 3.0 and have not had any problems whatsoever. MPG was about 27 average, shooting/fishing off road, short journeys and Mways.

The later 3.0 MHEV is even better though with real (not what the car tells you!!) mpg average about 32  All LR cars from 1984
2021.5 Vogue SE D300 Carpathian Grey
2018 Vogue SE British Racing Green GONE

Well I ended up pulling the trigger this afternoon and went for the PHEV! Would have preferred the grey colour version which I was looking at but it’s ok in this shade. Someone loved it anyway as the had the entire car PPF’d!

Now the interior is a bit, erm odd! Personally when spec’ing a new RR, don’t think I would choose navy interior!

Click image to enlarge