Trouble starting from cold, p0670 error

hi guys, got a clio1.5 dci 55 plate, past few weeks its got really hard to start from cold, turning over for like 7-8 seconds before it usually starts on a morning, once its warm it starts perfectly after that. I noticed what i think was a misfire on idling after starting the other day, this went away soon as the engine was warmed up also.Drives as normal other than that. So i bunged on one of those cheap odb diagnostic things and got the error p0670 glowplug control module. You think glow plugs need replacing? If so is a longer than usual socket needed? (sure i heard that somewehere??)



thanks for any replies guys.