My Q5 suffered sudden loss of power and I've been told today by my local dealership that I need a new turbo at 39,000 miles and a cost of 4K. Surely this is a low mileage for this to happen at and I am a fairly sedate female driver 🤣

That's a remarkably low mileage for a turbo failure, so the diagnosis is suspect in my view. Take the car to an independant Audi specialist for another opinion, and even if the turbo does need to be changed his charge will likely be lower than Audi.

Thanks Cliff. I've contacted customer service at Audi as I'm reading that most turbo units last for the life of the vehicle. I've seen the turbo and it is damaged 

£4k, that’s daylight robbery.

Get the car recovered from the main dealer to a trusted Indy. Main dealer labour will be expensive, and depending on the actual turbo, then this company are supplying new stock that Audi would basically fit, whether Garrett, etc. https://turbo-diesel.co.uk/audi-q5-turbos/

Importantly, the oil feed line needs to be renewed, insist on it, as the union nut weeps. In addition, new gasket on exhaust manifold. Oils and filter change as a matter of course.

Thanks for this I'll look into it. I have contacted Audi customer service to complain about the turbo malfunction given the low mileage and the expectation that it should last pretty much the life of the car. Fingers crossed they are sympathetic 😕