I am looking for a white plastic strip or beading,It is to put where the kitchen and dining room wallpaper join.There is already a piece there which was put a few years back,but now need a longer piece.I think the one there now was bought a B&Q but the handy man (no longer around)got it for me.
Have found one on Homebase site but don`t think it is flat at the back(would not matter if slightly domed on one side.)
http://www.homebase.co.uk/en/homebaseuk/diy/mouldings/richard-burbidge-internal-angle-moulding---plastic---2400-x-18-x-18mm-904705
Without going to a DIY shed to see what they have for sale I can not answer with 100% confidence, but I'd be surprised if they have no such plastic moulding. If one doesn't another will. Or you could just omit any strip. Or get wood and varnish it.
At least here in the U.S., the wall tile section of any DIY store will have 4 foot long sections of such pieces. It's about 1/2 to maybe 3/4 inches wide, various patterns and maybe 1/4 to 3/16 inches thick. I used just such a piece to break up a monotonous section of wall tile in a bathroom make-over. The one I selected was a brown tone with a pattern but there were plain ones and differing colors. Some times called rope decorative divider.
I used this one when I was doing the same. It was cheap and delivery was to so I was happy with the end results. Media URL: http://www.buildingplasticsltd.co.uk/D-Section-28mm-x-5M-White-Kalsi-p/d28w.htm Description: