I think personally you want as much space between the joystick and buttons for a small CP like that. If you want to keep all of the buttons on the top of the CP I would suggest moving the coin/credit/esc buttons in the middle, something like:

If it was me though I would remove the coin/credit/esc buttons from the CP top completely and move them to the vertical face of the CP. You would be then left with more room on the CP top and I would do a layout like this:

I'm not sure if Arcade Depot give you the option to put holes in the front face. If they don't you could always put them in yourself or failing that I wouldn't mind doing them for you (I'm in the UK too

)
If you do put them in the front just make sure they don't foul on the other buttons. I would use Japanese buttons which are much shorter and definitely wouldn't foul but you
may have an issue with 'Happ' style buttons.