Boden has a huge range of petite clothes. As with all shops, some suit me and some don't. I find that the trousers are generally too straight up and down for me (big hips and thighs), but their jersey dresses are generally an excellent fit (I have a small chest, bit of a tummy, large hips and thighs, size 10-12).
Gap Petite have a huge range too, online only, but you can return to store for an instant refund onto the card you paid with. I find their fit quite generous. It is the only shop where I am a 10 on the bottoms. Huge range of trousers, make sure you buy with a money off code.
Next petite are ok for jeans, I've found, especially their high waisted ones. But I don't think their quality of trousers would be good enough for me for work.
M and S petite are hit and miss for me. I check their stock online all the time to see what has come in new. I've been quite lucky in the past with jeans and work trousers, but the stock is variable. They have a good range of sizes and styles and lengths though. I am 5 foot 1 inch and I vary between their short and standard lengths. Their extra short is way too short for me.
Other stores with petite ranges are Dorothy perkins, wallis, new look, petite collection in Debenhams and principles in Debenhams, and asos.