Have I got enough pins in my Uno or should I use another board...?

Projects General Guidance
2

As you say, 8 inputs, 8 outputs, 2 for serial for networking - leaves 2 for display.
Use an I2C interface display.
http://www.newhavendisplay.com/serial-displays-c-253.html

Code will transfer easily to 1284/2560 based boards.

Are the sensors digital? Or do they have an analog level you want to monitor?
Uno only has 6 analog inputs broken out in the 328P DIP - if you use an SMD version in 32 pin TQFP, all 8 analog inputs are available.

Pumps will need some kind of buffering - simplest is controlling an NPN or a Logic Level N-channel MOSFET to connect - of pump motor to Gnd to turn it on.