The suggestion of using the 2 Pole Switch is great!
Be sure to use a 2 Pole Switch, not just a Single Pole Switch - since the Ballasts' will have 240 VAC Input.
Using only a 1 Pole Switch will leave a 120 VAC Ungrounded Circuit live at the Ballast, unless the 2 Pole Circuit Breaker is thrown to the Off position.
Best not to Switch from the Circuit Breaker - as this relies on you traveling to the Panelboard each time to throw the breaker.
Also, your make / type of Panelboard may not have Circuit Breaker Frames which are Switch rated (SWD).
Repeated throws of the Breaker's handle results in wearing out the device prematurely.
No need to use a Contactor, unless you plan to control them via low voltage means.
You could use a Contactor - even if the Control Circuit will be 120 or 240 VAC, but it's kind of redundant!
As far as noise, you may experience some noise when the Lamps first start (initial arc), and possibly when trying to restrike.
There will be a few levels of Harmonic Distortion throughout the operation - which is bound to happen with these L-C devices ("L-C" being Inductive - Capacitive, not Line to Common!).
Filter the inputs of sensitive equipment with typical AC Line Filters - PI setups with Inductors on both Input Lines.
Keep the HID equipment within a metallic enclosure, and be sure it's bonded with a solid EGC. This will reduce a lot of free floating noise in the close vicinity.
Should not have too much trouble with noise, but then again when circuits and elements resonate, funny things happen!
When and if they will resonate is a crap shoot!
Feel free to ask questions, as my reply only carries brief and basic data!
Beware, I can make this sound like Rocket Science!!!