Ok we're back up and running, realised that one of my resistors blew at some point (bit worrying but I think we're ok, might also have been disconnected slightly because I was messing around with the sensors. Basically the way I had the print object wired meant that it needed both sensors to send info in order to print (hot and cold inlet on the {list} object). Since the main sensor wasn't sending info because the circuit wasn't complete, I wasn't getting any printed messages, and because the main sensor is what actuates the solenoids, thats why they weren't getting any messages 🙂
Sorry for all the posts, but it might help someone in the future, and is also helpful for my writeup next week.