What to wear when the dress-code is casual, yet made up?

I'm 20 years old, and have, been invited over to dinner at the neighbours' house. We just moved here, and the entire street will be showing up. Thing is, it's quite a posh area and for the most part I feel very out of place her, and now I don't know what to wear? It's an "over for dinner" look, but where I'm from, that means jeans and a t-shirt...I doubt that that's the code here... so any tips for what "casual wear" is for the posh brits?What to wear when the dress-code is casual, yet made up?
wear a silk shirt with jeans and high heel shoesWhat to wear when the dress-code is casual, yet made up?
You can turn "casual" towards "elegant", without it being very noticeable, if you wear a dress. It can be simple, solid color, a little over the knee. Something like these: http://www.victoriassecret.com/ss/Satell鈥?/a> or http://www.victoriassecret.com/ss/Satell鈥?/a>What to wear when the dress-code is casual, yet made up?
not that i know anything about posh brits, but i would wear nice looking trousers and a pretty blouse. a chunky necklace or other jewelry. clogs or some other type of shoe that is comfortable, but nice looking. not sporty sneakers or anything like that. whatever you wear, try to look comfortable in it, like you didn't try too hard.
Just a nice skirt and blouse would do fine.

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