There is an increasing amount of Karen Millen clothing & shoes being copied and sold either direct from China/Singapore, or from UK sellers who have bought in bulk.  Things to watch out for:

Quality of material is far from original - Most stores can verify this.  Comparing the weight and feel of the fabric to originals really shows these fakes up to be the rip offs that they are.

Labels attached - KM have a orange and blue tag (sometimes just blue though) - the orange one has a price label on it in authentic items.  Fake items tags are slightly discoloured and thinner cardboard - the one I saw had fine lines through it.

Clear poly bags - they often come straight from manufacturer in clear poly bags with Karen Millen printed on & Made in China

Sometimes when a seller states 100% authentic or your money back! Obviously appears suspect.

Past & Current Seasons styles.  Styles made years ago suddenly become available in their masses!  This is simply not possible, unless someone bought multiple styles and siuzes and stored them for years.  Ex.  Pink Butterfly Dress & Shoes (LEONA) Black bow Dress (Davina) and now the Orange version, Antique Tulle Dress (used in campaign)  Black Satin Wiggle Dress (V popular )  Black & White Bow Dress etc..  Black satin dresses with roses around neckline.  Grey/Black Ombre Silk dress.  Chiffon applique dresses in all colours with silk roses attached.   Styles that were very popular in other words.  They know they will always sell!

Tax/Import Duty when bought from China/Singapore - Even if the parcel is marked as a gift Customs are still very hot on parcels recieved into UK.  They are within their rights to slap a big charge on your item.  I bought some make up from US and ended up paying more than double its cost in duty.

I have unknowingly bought 3 fake items in the past - A black Satin wiggle dress - ( I have the gold version) the quality is so poor in comparison.  A Black satin shirt - cuff links snapped on first wear.  In all cases I have been refused refunds.  KM head office unfortuanely cannot help either - which makes it difficult to make a claim through Paypal.  Extremely frustrating!!