Um... wow. I remember asking a similar question to this on a DC-focused website last summer when I was brand new to comics, and all I got was abuse for not knowing less popular DC characters. Here you've all posted really well-thought out, structured comments iwht Amazon links that must have taken you a while to sort out. Thank you.
As per your recommendations, I've ordered the first 3 issues of the current 'Avengers Assemble' series along with Straczynski's Thor Volume 1, Morrison's New X-Men Volume 1 & Iron Man Extremis because I like the premise.
Thanks guys - I'll be sure to bear this in mind when buying in future - seems like I have a lot of awesome stuff to read!