Please help dress a frump I for a wedding with a colourful cocktail dress code 🙏

[Connachtfive]

Hello you lovely stylish people.
Im the frumpy aunt. I want to be the stylish aunt. Please help. I’m 60. 5ft 4inches. In reasonable shape. I’ve no idea where to start with the colourful cocktail dress code. The wedding is in London in August. Budget up to £300. I’ve been procrastinating so any ideas, styles and tips very gratefully received.

Is it a day wedding? Evening do? Both? If it’s both, can you get changed or will the outfit transition?

@Connachtfive the Boden one posted above is fun for a summer London wedding

@Soonbbbqweather Cocktail no longer means shorter - just shorter than full length! Not above the knee anyway. Very few dresses are shorter now - they are mostly midi. I see shorter ones have been posted but I’d never ever wear any of them and harp back to the 60s. I don’t know anyone my age who would. The main element is to have the dress embellished by using an evening type fabric or adding beads and decoration. Midi for the middle aged though!