A member of the Simple Savings website that I am a member of has just confirmed with Cadbury that the vegetable fat they have just started adding to their chocolate is :
"5% vege fat - combo of palm oil and 'exotic' fats - shea, mango, sal and illipe"
Shea, Sal and Illipe are all considered tree nuts (albeit exotic ones we don't normally come across here)

There is no change in the allergen statement on the bar

(I have not noticed any change) and as far as I am concerned this is now a product which has nuts as an ingredient not just a "may contain traces of" product.
We don't give DD cadbury anyway as we consider the risk with traces to be too high, but I have heard of some nut allergic people eating the plain dairy milk chocolate due to the manufacturing process with the plain choc making the risk low (ie large batch made on clean equipment before flavoured ones made). I wonder if these people realise the risk has changed.