Turbopower 2
There was indeed a grey basic Turbopower 2 with Permabag as standard. I seem to remember it was a bit darker in colour than the standard "Autosense" model. Apparently purchased via a home-shopping catalogue.
It belonged to a work colleague, who then got laminated floors, and passed it on to me. I cleaned it up and passed it on to another colleague who's existing hoover packed in.
I had a Turbopower 2 Autosense, with piston bag-check indicator. The piston wasn't any real use, and dust eventually clogged the mechanism. My brother then had it for a while.
My mum still has the Turbopower 3 with Autosense (lagoon green metallic, no permabag). She used the tools a lot. The constant flexing of the bag door eventually weakened it. It split several inches above and below the decal that replaced the piston bag-check. Probably the problem was full power with scabbard crevice tool = stressed bag door. Fixed it with Sellotape!.
The activator/agitator is no longer available for this series of machine. Hoover-Candy told me that they tried to source an alternative, but no luck.
I'll bet that had it still been proper "Hoover Ltd", the part would probably still be obtainable.