Dress tips for office Xmas party please!

[mojoawol]

It's a proper dressy night out, not been to one in years, 43 so don't want to look like mutton, but nor do I want to look like a middle aged frump.

It all depends on what you feel comfortable in. I prefer dresses, so always wear a dress, whereas my best friend prefers trousers and top, so will go for smart trousers and a nice Xmassy/sparkly top?