Also, i'm no further forward with this lol
If you are buying a pre-made cabinet, its fairly easy. This is what I would do/have done in the past:
1. Lightly sand the faces you want to paint (presumably just the door and side panels) to create a key, and then clean with alcohol based cleaner and lint free cloth, or paint prep wipes.
2. Get some rattle cans of grey paint primer, and spray it with a few light coats.
3. Once cured, give it a very light sanding with fine sandpaper, and clean with some alcohol cleaner and a lint free cloth or paint prep wipes.
4. Get some more rattle cans of your chosen colour and finish (matt is more forgiving), and apply several light even coats.
5. Let it cure and polish with a duster and furniture polish.
6. Assemble your cabinet.
Failing that, contact Aquariums4Life or a local furniture maker, and get them to make something up for you in your chosen finish.