That doesn't sound like the worst thing in the world, I would have thought used 'boxes aren't that rare either.
My Zaf B is the 1.6, so I figured the extra mass Vs the extra 20 horses would about even out. Plus, it's either me on my own in there, or it's full to the gunnels with family and stuff, and in that scenario, any speed over about 65 seems to trigger a loud whine from somewhere in the region of the back seat.
Used boxes that aren't shagged are as common to find in breakers as Jaguar Ingenium 2 litre diesels without piston/valve intimacy...
And that includes other marques, such as Alfa, and everyone else using that chocolate box.
When they picked up my Zafira, the car transporter was full of Insignias and Astras about 8-10 years old, se did say all of them have faulty gearboxes
But sounds like you are edging towards the 1.8, which I think isn't a bad compromise of engines available.
When we looked at Zaf-B's last year, underneath every single one was rotten (and about 2/3rds of them had telltale signs of shagged gearboxes!), which surprised me, given how good the Zaf-A we had was in this respect. The only corrosion protection I ever did to our Zaf-A was clean up the brake pipes and grease them up. Here's hoping the Zaf-C is better in this regard.