Suggestions for "dress code suits"?

[ClothesClueless]

I have to go to a big dinner (prob hundreds of people, most of whom will be more at ease with what to wear when than I!) for which the dress code is "Suits".

Debretts decodes "lounge suits" as "For evening events, a smart, or cocktail, dress (with sleeves or a jacket) is a suitable choice." (but maybe "lounge" changes it, who knows?) while this chat thread seems pretty split...

I rather doubt I have anything suitable. Don't mind wearing dresses, but hardly ever do, so I have some that I think are probably not formal enough (Phase 8 skater dresses and the like) and some that might be too dressy (long or sleeveless or silk or all three - jackets don't usually work well for me as I have wide hips and narrow shoulders, so if I have to have covered arms I'd prefer sleeves).

I'm in my 50s, size 12/14, 5'6", pear-shaped more than busty; and though I often enjoy wearing dresses when I do so, I'm not a very "feminine" type, eg never ever wear makeup at all (and won't), hardly ever wear jewelery, and can't walk in high heels, so most "dress it up with" suggestions will cause me stress. I'd prefer to have a dress that will be right without much faffing, feel comfortable in it and forget it. Don't mind buying the right thing, preferably online, say up to £150.

Any suggestions? TIA!

I like the silk tunic and the shorter blue fitted dresses, agree you have good legs don't cover up!

I think the phase eight sienna dress looks 'suitable'!

Very interesting comments, thank you all again. No, I don't think I ever have worn a dress shorter than the shortest of these - have always been rather self-conscious about my legs (but found turning 50 quite liberating as allowing me to leave behind the idea that I should look like a 20yo :-) ). Thank you for the suggestion, I will bear it in mind for the future.

I wonder how many other mnetters will be at this thing? If NPD at E means anything to you, come and say hello to me and mention mn ;-)