OK I am recommending my own company,

W&Co (
www.w-co.co.uk), but as I am reading this message it would seem silly not to.
W&Co offer good quality Flex Face light boxes, see
http://www.w-co.co.uk/flexiface_light_box.php
If you check out the 'Gallery' page
http://www.w-co.co.uk/flexiface_light_box_gallery.php you will see photographs of Flex Face light boxes we've produced for Harrods, MINI, Swatch and British Airways.
For indoor applications it is also definitely worth considering the Fabric Face light box for easier graphic installation, for more info see:
http://www.w-co.co.uk/fabric_face_light_box.php
Feel free to call 0845 6 25 35 45 for further help or advice!