I'd just like to second Todd's recommendation of Blue Peace. I dove with them back in August and was pleased. The one thing i should mention is that we had students on board each time I dove with them. It's not a big deal to me, since I just want to dive, but if it is to you........
As far as who to stay away from, Aqua-World. Unless you just want to get in a late dive/night dive and can't get something else going, then avoid them. They load the boat till there is no room left.
I don't remeber Blue Peace offering a package, but they may. You should email them and ask. Their website is at
http://www.bluepeacediving.com/.
Their boat is a 6 pack which is one of the reasons I perfered them. They will however take a max of 8 divers, and it is a little crowded with that many on board. Entry is back-roll over the side. When you get back to the boat, you'll remove your gear and the DM will hand it up to the captain, and then you'll shimy up the short ladder.
While I didn't make the rip over to Coz, I dove with a couple that did the day before, through Blue Peace. According to them, the trip was long but worthwhile. Blue Peace provides the transfer to the ferry and has someone pick you up in Coz. They don't operate a boat out of Coz. they use another operator there. I forget who that is, but they will tell if you'll ask.
As far as sites go. If you like wrecks, they have a few that are suppose to be good. I didn't get to dive them due to students being on board and strong currents, but if you have the people willing to go, Blue Peace will take you. I forget the names, but they'll know what you mean. The ultimate dive would probably be the UltraFreeze, which is another wreck dive, but they won't go there unless they know they have an experienced group. The DM told me that about the only they do go there is if a group books the boat and that's what they want. Course you can always ask and see. We ended up doing all reef dives, and you can read my report at the link below.
PS...I removed the double post for you, since I saw that you reposted it here.