Sounds cool, I'd just go and have a look at the duplicolour rack and see what takes your fancy.
They do mix some paints on site at my SC, but I'm not sure if they do pearls or any other effects paint, you might need to go to an dedicated paint supplier. A quick google shows a couple of places such as Auto Paint Supplies in Fishwyck.
It won't be very cheap to get a can mixed up, but at the same time, you won't need much.