what i would recommend

Two of my favoured retail sites are Asos and New Look.
they both sell reasonably priced clothing and their sizing is fantastic, it is literally what you see is what you get. the clothes they stock are very diverse which allows the suiting for most individual styles.

The only downside to new look is the clothing lines they do stock are only their own which creates some limit but allows enough freedom so that you will not feel that you are following a particular trend.
Asos on the other hand not only stock their own lines but also stock other designer labels such as: firetrap, allsaints and bench to name a few. Asos also have regular sales which often allow you to snatch that designer bargain youve been longing for.

Primark (unfortunatly no web-site) often have a wide variety of clothing at low prices but often is the case that what you pay in price is what they return in quality, for the odd item here and there or just for that one-off, primark is your place