I have checked with Aurifil and have been pointed in the direction of the following two UK shops:
New Threads Quilt Shop stock every weight of Aurifil thread in a wide range of colours as well as carrying colours cards and some of the wonderful Aurifil 12 spool collection packs such as this Sarah Vedeler collection which pretty much holds all my favourite colours in 50wt:
The Button Company stock Aurifil wool 12 wt - which can be used for embroidery, hand quilting, cross sticth and also machine quilting - in a whole array of colours.
Of course anyone going to the Festival of Quilts can stop by stand G10 and choose Aurifil threads to their heart's content. I should also mention that Sarah Vedeler one of the Aurifil Qualified Master Designers: Sarah Vedeler will be at Quilt Direct's booth (C41/E40) demonstrating her embroidery with all her Aurifil kits collections available.