Just thought I would share as I know I'm not the only one who struggles to find narrow fitting plimsolls.
Last year we searched every shoe shop, clothes shop and supermarket for plimsolls to fit DD E width feet with no luck. Even clarks and startrite had nothing. In the end she had a pair of clarks doodles in non appropriate colours (I spoke to the school first) as in our school they were plimsolls as indoor shoes every day in class.
I was in Asda last night and got DD to try on a pair of plimsolls (fully expecting them to flap around) but to my surprise they fit perfectly. They were £3. I bought 1 pair but I think I will go back and get a spare pair and possibly the next size up too (I find this type of shoe falls apart quickly when worn every day). As I said DD is an E width so if your child has a narrower foot than that they might not work - it is worth a try though. I also didn't check the boys 'traditional' style only the girls ones. They are a Mary Jane style with a velcro strap.