And this opens the door for the perfect opportunity to drive home a few salient points...
All of our cars are noting more than machines with a pretty skin (in the case pf the Mondeo and others, "petty" can be sunbjective). Just like any machine, regular maintenance is required and just like any machine, it should be inspected before each use... Now, I'm not saying get down in the dirt and crawl around, but I am saying walk around the car and look closely - in the case of tires, we should make the effort to view the entire tread face as well as the sidewalls. The task that tires perform is fairly important.... (some niggling little thing like holding the car up off the road).
It is difficult to tell from your post if the tires are the originals or have been replaced in the past.... Since the car has over 100,000 kms on the odometer and the tires were "sound" 3,000 kms ago, I am left thinking that there has been some sort of suspension failure in the intervening time to drastically affect the tire wear. This would have us think that the operator is remiss in having things address in a timely manner...
There is another, more likely, scenario... 3,000 kms ago, your rear tires were removed by a tech with either a bad case of tunnel-vision or an inexperienced tech that felt that the good part of the tire meant it was "good" rather than the bad part meaning it was "bad" (don't laugh- both inexperienced techs AND customers alike don't realize that a tire is only as good as it's weakest part).
A third, almost unthinkable, possibility exists.... but I would find it difficult to believe that there is a shop anywhere that would fail to use a golden opportunity such as your situation to sell a pair of tires and a four wheel alignment. For a conscientious shop that charges fair prices (no, let's not go there...), such an opportunity is like cash in the bank.
Now, which "scenario" to pick? Every last car on the road is, intrinsically, unsafe. Safe motoring is more a function of the operater than the car. Ford, in north America, loves the dickens out of negative camber (improves cornering ability and feel) and factory settings often approach "way too much" (with the spec window being, sometimes, ridiculous). For the rear of the Focus, for example, Ford now supplies an upper rear control arm to move rear camber 1 full degree towards positive. Every motorist and every technician suffer from the "human condition" - making us intrinsically unsafe...
You appear to be needlessly agitated by your experience and I hope that you have come to the realization that your car is, indeed, a machine and requires constant monitoring to remain in a safe operationg condition....