Hiya,
Sorry for late reply, been sooooo busy this week.
Yes N18 is a more reliable engine, however we will happily sell N14 car, but we check them meticulously beforehand. Its like anything, read the moaners forums and you'd never buy anything. We explain to each customer that the engines are common for oil consumption, keep an eye on it, keep it checked and serviced and you should be OK. Its when people hear a rattle and keep driving the thing for 2 months and then wonder why the chain snapped??
We got lucky this week with 2 2010 purchases from Scotland that we thought were N14's that turned out to be early N18's
We walk away from more cars than we buy, because we are selective about what we sell, but we don't always get it right.
I'm much more comfortable buying N14 now I have my own technician. I'm just doing a HPFP in an N14 JCW that would have cost me £1200 a year ago. Same job now, done in minutes for less than £400.