Two friends alerted me to long, multi-part documentaries on D-Day.
One is running on public television here, so you in the UK may not be able to see it. It has lots of interviews with veterans done 15 and 20 years ago, woven in with film of the places and moments they discuss, right down to taking out an 88mm cannon or pillbox.
D-DAY: THE PRICE OF FREEDOM | American Public Television
The other is on The History Channel, and is available as a set of DVDs and as streaming video over the Internet.
There is also one I have not seen on WWI, with lot of coverage of The Somme.
D-Day - World War II - HISTORY.com