Fox glow plugs are excellent. I have been using them for so many years I forget when i started, maybe back in the early seventies or later.
The 2.0v plugs work great off of a single lead acid battery cell. I ran those plugs for quite a few years using a single cell myself.
I still have some, but I haven't used them since my last lead acid cell finally gave up the ghost.
I see no reason to buy more expensive foreign glow plugs unless you are competing and need the slight edge they might give you in a competiiton.