The cylinder head gasket was blowing when I bought the car, and grew steadily worse during my three months of ownership. In the end, it was drinking a gallon of water every fifteen miles, most of which was being sucked into the engine and blown out through the exhaust.
The steering box was on its way out at the same time, leading to rather vague steering.
The brake pipes were badly corroded and would certainly have resulted in the car failing its next MOT had I kept it.
The timing chain began to rattle, but would probably have outlived the rest of the car.
When I bought it for £250 (from a rather unreliable local ex-Skoda dealer), I tried to stick up for it in the face of the usual anti-Skoda prejudice. Unfortunately, its reliability record seemed to justify the criticism.
However, it was not the fault of the car (Skodas of this era were actually over-engineered, if a trifle crude & agricultural). The main culprit was the price. People of limited means often bought them for the kudos of having a new car, but then had no money left to maintain them. My car came with a full service history, but this had been signed by the original (elderly) owner up to 50,000 miles - after leaving the showroom it had obviously never returned to a Skoda dealer. I am sure that I bought it in 'original' condition, even down to the original engine oil and brake fluid!Let's face it, even a VW or Toyota would fall to bits if it was never serviced in 80,000 miles!
In the end, I had it re-MOT'd by a reputable Skoda dealer (it didn't need an MOT, but it is a cheap way of getting a vehicle condition report). When I went to collect it, he made that whistling noise that only an MOT tester can by inhaling through his teeth and gave me a list of several dozen failure points. I then took this list back to the dealer I bought it from (ensuring that his showroom was as busy as possible at the time), and demanded my money back, which I promptly got.
On the plus side, the driving position was spot on, the seats were comfortable and it handled surprisingly well, despite the rear engined layout and the wonky steering.
One odd thing about these Skodas was the way that the (front) boot didn't open in the conventional way, with the hinges in front of the windscreen, but from the side. As they were built in a left hand drive country, the hinges were on the nearside, meaning that in the UK, when parked on the left hand side of the road, you had to stand in the road to load it up. Hmmm, safe (not!).