Thank you both for your replies. I've not gone to any scrapbooking shops to look at the papers, but from just visiting antique stores and eBay, I'm amazed at the prices of wallpaper, as I thought it was expensive to buy new, but that doesn't compare to the old stuff! Goodness me, I have a few roles of paper, but all have glue, funny how wallpaper is out of fashion today.
From what I gather, people buy the old stuff today for boxes and picture frame art, which is a good idea if you want an aged look, but far too pricey for simple envelopes. Again, many kind thanks for writing.