So my Pi Zero came in about a week ago. I've put an image of Raspbian on an SD card and borrowed a USB hub for the keyboard and mouse. I really wish I had some spares but I'll just bite the bullet and take them off my PC temporarily.

I took Bharbour's advice and ordered a peristaltic pump. It won't arrive potentially until September. I guess that's the downside of ordering from China. Until then I'm going to put together the bones of the control software in C++ and check the GPIO output with a simple multi-meter. I should put up a Github repository to share the bit of code it should take, just in case anyone is curious.