Thankyou vauxhall for putting the throttle body in such an terrible position on this engine :D
First gain some access....
Remove the battery,
Drain a couple of litres of coolant and remove the coolant expansion tank (i siphoned it and ended up with a mouthful :o),
Disconnect the wiring plug to the igntion coil, then undo the 3 femal torx bolts holding it to the head. Now move it to one side (with HT leads still connected)
Now we have access we can get going. Undo the male head torx bolts that hold the top inlet manifold. Then you need to undo the 13mm head bolts that connect the top inlet to the throttle body. Disconnect any vacuum pipes and note where they went. Now lift off the top inlet manifold :)
Now disconnect the throttle linkage (there is a pin on the ball joint you have to remove to get the throttle cable free), and the induction hose that goes onto the throttle body. Now there is 2 coolant pipes at the bottom of the throttle body that you will have to disconnect (now you will be glad that you drained some coolant :D). With all this free you can rotate the throttle body and pull it up. Now disconnect the wiring to the IAC valve and TPS and its out...
With the throttle body out you can remove the IAC valve (2 bolts) and the TPS (2 bolts) and replace them with new ones.
Re-installation is the oposite of removal but use a new throttle body gasket and new top inlet manifold gasket. You might also want to clean the throttle body while you have it out using a carb cleaner.