i would like to buy a new grass box for my Atco Windsor 12s mower

Hi, welcome to GoY, although a number of garden centres advertise on here, we don't actually sell anything, we're just a group of people with an interest in gardening, having said that, I have tried to find a grassbox for you, unfortunately that particular model appears to have been discontinued, it hasbeen replaced by the Allett Expert Kensington 12 E.
I have found a couple of phone numbers for you, Just Lawnmowers sales advice. 01263 820202 or you canphone Atco themselves on 0845 601 4944 for more information, Derek.