Or rubbish compared to the likes of Denso or Bosch etc. I know it's not something you but regular but would like it last more than a few 1000 miles.

No experience of Nappa, however, if it's for your 4.2, have a good look around eBay and you can usually get a Denso one for around 100 - 120 quid.

 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior
2013 Range Rover Sport SDV6 HSE Black Edition in Santorini Black with Ebony Interior

Ok
Cheaper for Denso so far is £235.

Having said that I'm now thinking of going back to the devils fuel and an old td6 but not sure.
I'm a very indecisive person, it's bloody annoying.

I bought a NAPA battery and NAPA alternator for my 4.4 TDV8 - I do have a local branch to me and buy lots of stuff from them for other cars, got to say both items have been fine so far, it was about 12 months ago, so pretty happy with them

Yes I've heard mainly good reports of the make. It's mainly that they're was a TMS factor not far from me but now NAPA and thought who the hell is this.
I can only get Denso or Bosch online now.