Reverting back to default drivers - mac


I'm helping a friend with a project and had to install the CH340G drivers from here to be able to use her Chinese nano clones on my mac (Yosemite):

Now I'm trying to use my own boards, but they're not showing up on the serial port list! Previously they worked fine with the default drivers.

Would the CH340G drivers have over-written the original ones? Can anyone help me re-install (if that's what I need to do) the original drivers so I can use my own boards again, please?

I'm away from home so can't connect to TimeMachine and also a bit of a mac newbie generally.

Thanks, Nikki