Tried out a few options with castors but it just wasn't looking right, so I left it as it is for now.
Got the PC all set up, it's running MAME via MaLa and it's running beautifully; 28 seconds from switch on to MaLa game menu.
Top drawer contains the PC with speakers, mouse and gamepad. The keyboard is accessible from the lower drawer.
Although I was considering arcade stick type controllers initially, I'm finding it a lot easier using a pad right now, especially if I need to switch orientation for hori games. I'm using a MadCatz SFIV fightpad and it's working brilliantly, going to purchase another for use as the P2 controls.
Gone with a nice red MaLa layout and red mouse mat to match the decor :)
Speakers are USB powered, the monitor and PC are connected via a "Y" double kettle lead, so the whole unit connects via one mains plug, power on for everything is triggered by the PC power button.
Jobs to do include an external power button and USB socket(s) mounted into the unit for controllers, flash drive etc.