Same from me, get some good ones. You may get good at doing it if you buy cheap ones but I'm sure your P38 has other things to absorb your time. It was only after I realised that I was changing the same two cylinders every few weeks using up six Britpart cheap-oes from Ebay that I got some from the local factors - Lucas on the box. And they've been fine through the recent minus weather, starts first time every time.
Having a hot start relay tends to give them a hard time. Mine got reluctant to start with only two plugs down. There's lots of threads on here with advice on how to do it, have a browse on the search button.
Here at LandyZone we have plenty of very knowledgable members so if you have any questions about your Land Rover or just want to connect with other Landy owners, you're in the right place.