The DVD with McMillan's voice-over was never made available for sale. It was given away free with a magazine called Country Walking many years ago. The best you could how for is if someone on here has a copy they could offer you.
In the meantime, I can recommend my guidebook - and if you clink on the Google Books link, you can read the whole intro and get a sample walk for free. Can't do links on the system I'm using here on my desert island trip...
http://www.paddydillon.co.uk/guidebook/the-pennine-way/