This is a fantastic thread. It's amazing to read people's recollections and see so many photos. My only experience of meeting Darth Vader was when he visited Debenhams in Romford. A photographer from a local newspaper set up a photo of all the children surrounding Vader. Me and my friend were too cool to take part but my younger brother ended up in the photo. The paper got thrown away before we could snip out the cutting but hopefully I'll be able to find that issue again.
I covered the Darth Vader tours in my book The Star Wars Phenomenon in Britain (if a small plug is okay). In 1977/78 the Rank Cinema chain commissioned some Vader and Stormtrooper outfits that they used for promotions, with the Vaders being pretty poor quality. Individual cinemas and department stores put together Darth Vader outfits too in '78. For The Empire Strikes Back some professionally made Vader Outfits by Nick Farmer and screen-used Stormtroopers did the rounds organised by Rank Cinemas, Palitoy and Lucasfilm UK. Palitoy also had a couple of Boba Fetts that they sent out. The Return of the Jedi tour was organised by a subsidiary of Palitoy's public relations company that used the Nick Farmer outfits. Lucasfilm UK also had a couple of the same Vader costumes that they could use for promotions. I interviewed some of the people who organised the tours for the book.
Memories fade over the years and people I spoke too didn't know exactly how many costumes were doing the rounds. I know that there were twelve Vaders in 77/78 constructed for Rank. Probably around 5-6 Nick Farmer Vaders in 1980 and about 20 from 1983 onward. Regular "actors" were often used, so some of the signatures will match. It would be interesting to find exact numbers one day or even interview some of the people hired to dress up back then. Here's hoping!