Okay, update from mechanics. 

Oil leak is from the camshaft sensor.   O ring seal removed and cleaned, and will be check at the next service.  No problem.

The other issue is much bigger.  "Intake system swirl faulty"  "Worn ball attachment to intake manifold, requires replacement intake manifold"

The quoted price is AUD2551 for a genuine Hyundai part, or AUD1785 for new old stock from a wrecker.  That's USD1658 and USD1160 for our overseas readers.  Very hefty price for something I didn't know was broken until another mechanic looked around the engine during an unrelated service.  The car burns slightly more fuel than it used to.  About 5.3K/100km instead of 5.1, but that could just be due to an aged engine.  It's no big deal.  Drivability is perfectly good.

I understand swirl control kicks in at certain revs and helps emissions.  Since there is no emission testing in Australia I can keep driving like this without legal problems.

I asked the mechanic if there is a risk of the loose components flying into the engine.  "There shouldn't be" was the answer.  Nicely couched in deniability if something goes wrong I guess.  I have read about BMWs with faulty swirl valves that fly into the engine and lunch the whole thing.

My swirl control is flapping about and I guess is fully open due to the natural flow of air.  I'm highly tempted to not repair this issue as it's so expensive, and I don't have any problems like check engine lights.  If it's broken then why doesn't the ECU throw an error?

Why is the swirl system so expensive?  Mechanic said you can't just buy the motor/valve part:  you need to buy the whole manifold.

oh man... that's pretty rough.  It sounds like the DCT was not the issue to start with. 
Why did they charge you $800 labour?  It's not as though you could have walked up to the parts counter and buy a DCT to fit it yourself as an option.

Ignore the warranty period.  You as the consumer have a right to expect certain things when they buy a product or service. In consumer law, these basic rights are called consumer guarantees.  Your rights are protected under consumer law and Hyundai can't walk away from it.

There is NO warranty period under Aust consumer law. Consumer guarantees are automatic and can’t be taken away. Warranties are extra promises that a business can choose to make on top of the consumer guarantees.

Hyundai has to remedy this either, replace, repair or refund.

Were you in Reverse gear?
My rear wiper operates when front wipers are on when Reverse engaged.

I'm at my wits end. I have a 2017 i30 PD, dual clutch transmission hatchback, and last year I had to have the entire transmission replaced after only having driven 30,000km (I am the only owner and don't drive it like an idiot). The issue was that the orange lights on the dashboard would light up, and when I put the car into reverse or drive, it would not move. Sometimes it revved, other times it did not.

The cost - which was covered by Hyundai, thankfully - was around $8000. I had to pay for labour ($800) 

Last week, I turn my car on, I have a dashboard full of orange lights and the telltale not moving when I put it into reverse. It's undriveable because it's not safe, and I've also lost power while I've been driving (really unsafe). I'm really not sure what to do if it needs *another* replacement transmission. Has this happened to anyone else? The odometer now sits around 32,000km and I find this completely unacceptable.

Photo for reference.