Shopwiki has a section in the UK, too. Just as their American equivalent, the site lists multiple webshops in various categories and at the moment these amounts to around 30 000.
Some examples: Check out these tips for buying sources of Casual Work Clothes for Women, Women’s Fashion and Trends and Women’s Suits. You will surely find something of interest here. Naturally, any male reader may also use this resource for finding appropriate gifts for that very special lady.
If we stay on the subject of clothes for women maybe I should also mention Petite Clothing for Women and Women’s Blazers. It’s all on Shopwiki UK.