The animated tivo opening losing sound halfway is normal, the original image is based off a US Philips Tivo so it was produced in NTSC format.

I think only the Thomson unit responds to the standby remote command, the rest you have to enter standby from the menu's.

I think your Tivo will be outputting S-Video or Composite via the scart, not RGB only the Thomson outputs true RGB.

It's entirely upto you if you want to go through the reimage process, I have only heard of a couple of installs with stability issues running a Philips image on the Thomson. You'd also then get RGB signal you want.
Out of all the Tivo's I have the Thomson is my fav.

Your best bet would be to try and reimage the 40GB drive you have with the Thomson image and see if that works, with the Thomson image there is a minimum size drive you need to restore to, I know it doesn't restore to a 30GB drive, you get the "Restore failed: First target drive too small" error.
I'm not sure what size it was created from. But give it a shot on your 40GB, if you get the error then you know the drive is to small for that image.