I am very of your height! I am only 5'3" and always having to shorten hems.
If I were you I would head to Zara, they have great stuff at the moment. Massimo Dutti is Zara's older more expensive sister and always has lovely things, really nice quality, classy but still on trend IYKWIM.
The big trends for summer are:
nude, Zara have lovely nude draped tunics and dresses, also pretty white embroidered tops and lightweight scarves which really finish off an outfit.
nautical, lots of breton tops in the shops, esp Oasis, or get a Petit Bateau one for authenticity.
Get yourself 2 pairs of jeans, one dark wash, one white.
Jersey blazers are fab, I bought two, one navy with cream trim, one charcoal grey. They look smart and are very comfortable.
Maxi dresses are great for relaxed glamour, I can't wear them, but they'd look great on you
Clogs are the footwear of choice for the fashionista this season, but they are too ugly for me, a pair of gladiators sandals look better I think.
It is bucketing down here today, so a smart coat is handy for summer, there are trenches everywhere this season.
Finally, a good pair of sunglasses and you are all set