As far as where to buy... since one of you who asked is in Canada, the other is in the UK, and I am in the US, you're on your own... start at
www.hella.com and find a dealer locator thingy for you country (if there is one, there is for US).
As far as wiring them up... anything is possible.
I haven't done mine yet. The wiring included with them has a three position switch. Obviously, one of the positions is "off". It's a fair assumption that one of the positions is "angel eye rings only". The thrid position? Could be driving lights and rings, could be just driving lights. If you wire them up as the instructions tell you to, it looks like you can put the switch in any of the three positions independent of what other lights are on. That means you can turn on your driving lights with no other lights on at all. In fact, I think you'd be able to accidently leave them on as you took the key out of the ignition and retired for the night, to awaken to a dead battery. Pretty dumb design, if you ask me.
My current plan is to keep the wiring from the PIAA lights installed, and splice into those wires to connect the Hella driving lights. That way, I keep the better PIAA switch. Then, I'd tap into the parking lights for the rings... Of course the leads are different between the Hellas and the PIAAs so I cannot just swap the lamps.
Or, I might not install them at all. I haven't decided yet.