New A7 Owner - A few problems - Help!

[Lewis-Oddie]

Afternoon folks.

I have recently acquired a 2011 A7 3.0 TDI Quattro and I'm having a few issues, hopefully somebody here will be able to shed some light for me. It's a bit of an exhaustive list so please bare with me! The first issue I've got is a weird whistling / humming type noise at a certain speed on deceleration. When travelling on the motorway, the car is fairly quiet but if I let go of the accelerator and coast, when the car gets to about 60 mph I get a fairly loud whistling type noise from the rear end which disappears at about 55. As soon as I touch the accelerator pedal the noise disappears or certainly quietens down to a level that I can't hear it anymore. When I bought the car, the seller advised it needed a couple of new tyres on the front and agreed to replace them. It actually ended up having 3 tyres, 2 on the front and 1 on the rear. On the rear, the tyres don't match and the tread levels are quite varied. Could this be causing the noise?

I'm planning on swapping the wheels around later on today to see if the noise gets any better or different. As a side note, my partner has sat in the back of the car and she said that she can hear a constant noise and her description sounds like a failed wheel bearing to me. I briefly jacked the rear end up and checked both wheels for any play at 12 and 6 but couldn't feel much play?

Whilst travelling on the motorway at weekend, I suddenly got a whole host of warning lights on the dashboard. Parking brake fault, air suspension fault, ESP Fault, TPMS fault. A quick google suggests it's linked to an ABS sensor but VCDS didn't highlight any faults with any particular faults? Would these faults suggest a wheel bearing fault?

Second issue is an oil leak. I changed the oil a few days after I got it as the MMI was showing the level as being just over the minimum. I must have only done 100 miles at absolute best after changing the oil and already it looks like it's dropped a touch. I also noticed some rainbows on the driveway floor yesterday but difficult to tell where it was coming from, if anything it looked like it had potentially started at the rear of the car and not the front. Are there any common failure points for oil leaks on this engine to check?

Finally, I'm pretty sure the engine mount(s) are shot. When stationery at traffic lights in D, there is quite a bit of vibration which can be eradicated by giving the car a tiny bit of gas. Having done some research, the mounts seem a common failure point on the C7 chassis?

[Crasher]

I poor (probaly Chinese) tyre can sound like a wheel bearing. Those engines are terrible for leaking oil from the sump lower section but sometimes also the upper which is a huge job you need it on a lift with the undertray off and also get a full VAG specific code read carried out.