I've started to compile a list - hope this helps! Feel free to update as you wish.
Spring/Summer 2015 Sale
Acrimony (DRKSHDW, Gitman, Robert Geller, etc.) – 33% off sale using FINALCALL (ends 29/05/15)
Barneys (Raf Simons, Margiela, etc.) – Up to 40% off
Blue Button Shop (Kapital, Nanamica, etc.) – Up to 40% off selected items
Carson Street Clothiers - up to 50% off
Coggles End of Season Sale on now! | Shop up to 40% off
Coverchord 30% off accessories and...