Take some time to look around the beauty page HERE, because there are some great deals to be had. But you should also note that some prices are NOT so great, because keep in mind that this is an international site, so some US brands will have higher prices than what we would pay here in the US.
As for UK-exclusive brands and products, there are plenty on sale. I've put together a little widget of some of the items that stood out to me, based on the current sale prices on the ASOS site and also based on the fact that many of these products are difficult to find here in the US (and if you can find some of these in the US, the prices are higher than the ASOS sale prices). There are also a few items that are readily available in the US, but the ASOS sale price was worth mentioning.
NOTE: Some items are not available for shipping to the US (mainly nail polish) so just look for that notation in the item listing. Obviously everything I listed below IS available for shipping to the US.
PS: As we all know, Vaseline lip balms here in the US come in little tubs like this, but in the UK they come in tins. The trio below is very difficult to get here in the US, and it's on sale right now on the ASOS site. You get Original formula, Rose, and Aloe Vera (not available in the US). Just an FYI to my fellow lip balm fanatics!
Click on an image to go directly to the item listing (direct links below widget).
Bourjois Healthy Mix Serum Foundation
Bourjois Bronzing Powder and Highlighter
Bourjois Color Edition 24HRS Cream to Powder Eyeshadow
Rimmel London Kate Nudes Lipstick
Barry M Lip Paint in Lavender
Rimmel London Good to Glow Highlighter & Contour
Simple Clear Skin Oil Balancing Facial Scrub
Barry M. Cor Balmy Tinted Lip Balms
Simple Kind to Skin Purifying Cleansing Lotion
Lottie Balm Ball
Rimmel London Kate Lip Balm
TheBalm the Manizer Sisters Trio
Illamasqua Limited Edition Celestial Palette
Eyeko Look Me In the Eyeliner and Say That Set
Bourjois ASOS Exclusive Christmas Essentials Set
Lottie ASOS Exclusive Beauty Essentials Kit
Bourjois Rouge Edition 12HRS Lipstick
Vaseline Rose Vintage Lip Therapy Tin