I believe the ECU itself is responsible for the cruise control and I don't think there's a fuse listed for it. It's also possible you may have a duff clutch switch (switches cruise off when you press the clutch in), which often manifests itself as a P0704 code.
Also, finished off the intake by running some hose from the filter to just behind the front bumper next to the intercooler, seeing as the top radiator hose wasn't agreeing with the placement of the Vectra C snorkel. Gonna be interesting to see how much gets done this weekend, as if I hope to get it on the road the following weekend.