Well due to the age of these vehicles they are becoming more rare to find at the scrapyards/breakers. So it is becoming harder to just replace the throttle body . and with another body that is potentially between 10 - 20 years old.
I drive the vectra b and the last few breakers yards i've been to, they say that they don't get them in anymore.
The vectra B and C have different mounting bolt areas so they are not quite the same. Got the same idea but not quite same shape.
I do not know the difference with Astra's Zafira's etc. The guy in the video is basically saying people are unnecessarily replacing the full throttle body.
When all you have to do is replace the black plastic side part. called a throttle position sensor kit. As the guy in the video points out it is the fingers that slide on the variable resistor, That are faulty, triggering reduced engine power.
After dismantling the whole body he finally identified this as the problem.
So rather than meddling with the accelerator position sensor, Which some people have done. Without any joy
https://z22se.co.uk/threads/pathetic-throttle-response-causes-solutions.28791/#post-1259134
This could be the answer. I see that
Graham2704 has a 2.2 direct with a poor throttle response which has no "go" in it anymore.
I would say there could be a connection here that needs further investigation
It would be interesting at least to open it up and see how it looks

.