my 3 year old 525d has just over 100,000 miles on it and recently i have noticed after several hours driving in traffic that the auto gear changes have become rough , in particular when it changes down from 2nd to 1st gear it would almost put you through the windscreen.I hope someone out there can give me some advice.

 

I think an oil change is due

 

From what you said, it might be the valve body.

 

Hopefully it's not too late with the "lifetime transmission fluid". It's a sticky situation at this point. There are two schools of thought, some believe that problems can be fixed on a slipping transmission by changing the oil, while others feel that it will lead to failure because new fluid will dislodge all the old sludge buildup which might be helping keep things together.
There is no clear answer. Get it checked out. If it warrants transmission replacement, it might be worth a try by changing fluid 1st. Check the DIY section, I just did a writeup on it.
Regards.
Raj