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There's a bung above cylinder 3, which is a good place to monitor as it's usually the hottest running. You'll need an adapter normally to screw the temp sensor into the hole.
As you look at the car from the front, it is the top left, i.e. drivers side and closest to the drivers seat. Takes an allen key to remove the bung, think it might be 8mm required. If you have a TMIC it's probably easier to fit with this removed.