2008 mondeo 2.2 175 burning smell

[spoonv6]

Ive just got a a mondeo titanium x 2.2 175 diesel. Firstly the car is fantastic but iv noticed a burning smell when i come to a stop. When the car has warmed up and i come to a stop at some traffic lights or round about etc a burning smell comes in the cabin. Firstly i thought brakes so they seem fine as i came to a stop without using them and the smell still came in. The clutch feels spot on and doesnt slip so i dont think its that. Ive read that it could be dpf but surly that wouldnt do it every time i come to a stop? The car drives like a dream with no warning lights. Any ideas?

[njw1]

Plastic bag on the exhaust? De-ceased animal in the engine bay?

[spoonv6]

Been to the garage. Oil leak dripping on the exhaust is the reason for the smell