Hi Paul,
Here is a link to a UK supplier but the image is a bit small. You can see the brown peel-off backing on the adhesive part.
http://www.staples.co.uk/office-supplies/filing-and-archive-supplies/lever-arch-files-accessories/lever-arch-accessories/filefix-self-adhesive-filing-strips-a4-clear-10-pack
I have attached below, an image which shows how I use them.
I have a home-made jig, made from hardboard, that locates the strip on 2 pegs and the A4 sheet with raised strips so that I get consistent positioning.
Terry