To test the valves
Hi Philip, as Rob says it's not the pressure switch or it wouldn't control the water level at any point in the cycle.
It seems to me,it is the cold fill valve, it doesn't fill with any cold water untill the conditioner rinse, where it takes in cold via a second cold valve. As a quick test swap the live connections of the two cold valves over, if its the valve, it will let in cold water at all the cold fill points but not during the conditioner fill. Obviously the water wont be entering the correct part of the despenser drawer, but it will tell you if it is the valve or the timer.
As another thought, check the connctor blocks are fully home on the timer and that the wires running round to the valve are ok, Like the rest of us machines are moved around a fair bit so wires can get dislodged.
I know your young and enthusiastic, but remember to unplug the machine before going inside, I learn't the hard way.
All the best for finding the fault
Mathew