Chad91

Hi there, Looking for a bit of advice and to see if what I have been told today sounds correct. I have got a 2016 320D Touring M sport which has done 55k. Over the past few months I have felt & heard a clunking/knocking noise through the steering wheel. This noise is a like a intermittent knocking and can be heard when driving at low speeds and when applying the brakes. It only also happens when the temperature is over 20 degrees ish or have been driving for over an hour. I cant feel the knocking through the pedals just through the steering wheel. My brother in law works in a garage and couldn't find anything wrong so I decided to take it to a BMW specialist today whilst I had an oil change. They couldn't get the noise to happen whilst on a test drive but could apparently hear a clunking when up on the ramp and i have been told I need a new rear diff costing £2300 all in. They also said all the brakes look fine as this is what is what I thought it could be as I can hear the clunking even more under braking at lower speeds. Has anyone has got any advice? Thanks in advance