I still think 10k is too much resistance for the pull-up. Try 2.2k. Although 10k possibly won't blow the P-channel if you don't "blink" the light, and/or it isn't very high wattage.
I also would use a BS170 n-channel MOSFET instead of the NPN transistor. The circuit could look almost exactly the same as the one for the NPN (you could switch the Arduino resistor to 1k, and might not need the pull-down.) But now I'm just being anti-BJT 