£100 to spend at Great Plains - what to buy?

[Silverstones]

I've got £100 to spend at Great Plains, but am rather unsure about what to buy.

I'm petite, size 8, 5'2'', a very young looking 40.

I could do with a new coat, but I'm not sure whether the ones they've got will swamp me.

Apart from that, my wardrobe isn't crying out for anything in particular.

I want to look stylish but (for work) professional. I'm very conscious that I look much younger than I am, so this could be an opportunity to add to my professional wardrobe.

Any thoughts, style gurus?