Thank you for your replies.
Sarah, after reading your message I dragged dh off to Derby to have a look at the shop. It never occurred to me that they had a shop and it was well worth a visit, thank you. I found that the coat I was going to buy wasn’t suitable and that I would wait for the new stock to come in and a 20 % discount was on offer, so thank you mountain mama. But actually, thinking about it, they had two waterproof coats in the sale in the sizes I wanted to might send dh to Derby to go and buy them and then buy the fleece jackets with the discount. As it is the rain coats that we so desperately need.
On trying them on I was surprised to find that ds1 (5.5) of slight build actually needed to buy a 6-7 (with room to grow) as the 5-6 was too small and ds2 who appears quite big and everyone tells me is going to be quite tall is actually only fitting the 2-3. So there we go!