I notice that using AV or TV mode that the meter sets itself to an "average" grey automatically smack in the middle. But using Manual mode, it fluctuates alot no matter what metering i.e. evaluative, spot etc, setting i use.

With Av or Tv modes, the camera adjusts shutter speed or aperture, respectively, to achieve a good exposure based on the metering mode you've chosen, so the meter normally shows a reading right in the middle of its range. With M mode, you're in control of all the parameters (shutter speed, aperture, and sensitivity), the camera tells you what the meter says without trying to change any settings to compensate. You're free to adjust any of those parameters to get the meter to read +/-0EV if you want to, but you obviously don't have to do that.

I notice that using AV or TV mode that the meter sets itself to an "average" grey automatically smack in the middle. But using Manual mode, it fluctuates alot no matter what metering i.e. evaluative, spot etc, setting i use.

With Av or Tv modes, the camera adjusts shutter speed or aperture, respectively, to achieve a good exposure based on the metering mode you've chosen, so the meter normally shows a reading right in the middle of its range. With M mode, you're in control of all the parameters (shutter speed, aperture, and sensitivity), the camera tells you what the meter says without trying to change any settings to compensate. You're free to adjust any of those parameters to get the meter to read +/-0EV if you want to, just as the camera would do in one of the automatic modes, but you're obviously also free to use your own choices for those parameters even if the meter tells you that it's reading more or less light.

Your camera provides a number of tools for working with the metering system. As described above, manual (M) mode puts you in total control. In Av, Tv, or P modes, you can use the AE-lock function to get the camera to pick settings based on the current metering mode, and then lock those settings in so that you can reframe without having the settings change even if reframing the image makes the meter read something else. You can also use exposure compensation to make the camera choose settings that make the image darker or lighter than it would otherwise, basically telling the camera "yes, I really do want the image that bright."

Is using AV or TV mode more dependable on getting a "perfect" average grey, since it sticks very well right in the middle of the meter?

Av and Tv are more dependable if what you want is a reasonable exposure, and those modes are more effective when you get the hang of using AE-lock and exposure compensation because those tools give you a greater ability to tell the camera what you want while still letting it adjust for changing lighting conditions. M is more reliable if what you want is to not adjust for changing lighting conditions, or if you're working in conditions that would confuse the auto exposure system.