I am biased as a former employee - I'd love one :) Aga own Rayburn BTW. (Aga will do hot water but not CH, and Rayburns will do both) Loads of info over on http://www.agaliving.com/aga-range-cookers
I'd go 3 oven (still a traditional Aga) with total control so you can control its energy consumption when your not in the house/out at work.
Oil/gas/solid fuel have been the traditional way of fuelling one of these things but if you do it that way, you need to consider what to do in the summer (do we have those anymore!) when its hot and you really don't want the Aga running 24/7 and pumping out heat all the time. What are you going to cook on?
Method of cooking is a bit different as there is more focus on the oven as opposed to using the hot plate (i.e. steaming veggie in the oven as opposed to boiling on the hotplate) but once you get your head round it or attend a free cooking demo (they do them all round the country) its not all that different.
You'll need to factor in servicing costs too.