Advice on Audi not honouring warranty

Hi Forum,

My wife recently bought a car, a few months in now, she started to get electrical issues with main screen, warning lights, etc.  Car failure meant a recovery job, and taken to Audi dealership for analysis and inspirationally repair.  They reviewed the issues, and said it was a frozen windscreen wiper fluid pipe that had burst and had been spraying water across the main management unit shorting the whole lot.

They apparently tested the fluid and it came back with only water, not anti-freeze mix.  Now my wife having only bought the car (unfortunately not from an Audi dealer), didn't even top up due to short duration from purchase to issues.  So they are claiming negligence and the £3k of damage isn't covered under warranty.

Anyone got any advice on this? We may be on to plums here! Surely pipes are manufactured to consider cold temperatures - it was only around -2/3 degrees max at its coldest over the last few weeks.

Thanks in advance.