From previous experience, glow plugs do little to nothing on common rails except in extreme conditions (i.e. sub 4 and/or sub zero) owing to the huge injection pressures. Normally a delay in start is attributable to rail pressure (either through regulator or sensor) meaning that the injectors are waiting to operate. In other words, fuel system gremlins!
Like I said, dealer is happy to look, but it's an inconvenience of about an hour to get there and back with a courtesy car, not something I want to repeat too often, would like to give the guy some sort of clues lol. I might hook it up to live data myself.