ECU is in that engine bay fuse box, just a good bit smaller so not as noticeable. It's just a thin ali casting mounted on a larger steel panel which lifts out of the fusebox.
You'll find 2 big multi-way connectors on it. Follow the loom leading from each. One of them crosses over to the engine cable tray and the other heads back through the bulkhead near the pollen filter. The connector on the end of the latter loom is the one you want.
You can remove the hood from the plug by removing a couple of screws so you can see what wires are connected to what pins. The pins on the connector are numbered on the base of the connector so you can count up and find pin 21 and see if it's got the black and blue wire attached.
It's possible that there's nothing connected to it on an auto loom, and maybe even no pin in the connector. If so, you're probably best just getting the config on the ECU set to auto. (I'm not sure what will happen when the ECU realises it can't talk to the auto box ECU via CAN, though). If there's a wire there you have 3 options:
1) Trace the wire back and see if you can find it emerging under the dash, then connect it to a clutch switch.
2) Cut the wire and connect the end that leads to pin 21 to the black wire from pin 47 of the ECU to fool it into thinking the clutch switch is present, then wire the actual clutch switch in series with the brown and grey wire at pin 1 of the brake light switch so the clutch will deactivate cruise.
3) Run your own wire from pin 21 into the cabin to the clutch switch.