Pillows are almost certain to be rectangular in the UK but are by tradition square in France. Having transported beds, bedlinen and pillows with us to France, this has caused a bit of a problem when needing new pillowcases. Some supermarkets sell a limited range of rectangular ones, but they are not easily available. Buying a matching set of new bed linen is a problem because the pillowcases that match are most likely to be square. “Je cherche une taie d’oreiller rectangulaire”, might be of use to you.