There appears to be a little bit of a glitch on the M&S site at the moment so you can order your school uniforms, add sale items and, when you use the voucher code below, you get free delivery plus 20% off the school uniforms.
M&S have a sale on their school uniforms at the moment with 20% off all the different sorts and types available on the site. This discount will help you save some nice cash on these expensive essentials and you can stock up for some time to come.
Once you have finished sorting out their uniforms, you can then go to the sale section, add some of your own items (or some summer extras for the kids) and, using the code UNIFORMS at the checkout, you will get free delivery on absolutely all of the items in your basket.
I have tried this twice and it has worked for me so get on over there and get shopping.
Thanks to shadow1 at HUKD!