Well what a night! (and why do I feel like I should sing that?!) We killed off Kil'jaeden in pretty short order to give us a full clear of Tomb of Sargeras, and earn us various achievements - personal and guild.
We then decided to turn right back round and start playing in heroic .. clearing the first three with little difficulty - awesome!
Massive well done to everyone who took part - big thanks also to Jandor who advised and kept a calm head when some of us were getting a bit excited :p (you know who you are ..! )