I'd say glow plugs to. I had to replace mine recently and it cured the problem for a few weeks. I bought cheap ones off eBay and I think they are fooked aldocents it dosent fire straight up anymore.
I find if I use a bit of throttle tho it starts easier anyway
Can't be bothered buy any more glowplugs as long as it keeps starting

Don't think common rail diesels need glowplugs anyway. They can start without just takes a while longer