Unfortunately Meyers went berserk in my game and kept running off and getting killed by geckos. He was at primm I needed to speak to him to finish the quest and he kept taking off back to ncrcf before I could catch him, so I used the console to reset his ai then he was fine. So the question is does doing this mean I wont get the achievement for hardcoe mode.

If you use a console command it disabled the achievement system for that session - but if you close the game and reload you'll be able to get achievements again.

To elaborate a bit: as long as you do not use the console during the session in which you finish that play-through you will get the achievement provided you left hardcoe mode on for that character's entire career. Exiting the game completely (i.e. to desktop) and then reloading your most recent save counts as a new session, so you could potentially use the console for that character's entire career except for the final quest. Of course, in any session during which you use the console even once you will not get any achievements, so doing so is probably not a good idea unless the hardcoe one is the only achievement you are after with that character, which is rather unlikely.