60th birthday trip cocktails dress help

[Mecheng2]

Help I need a dress to wear on holiday in uk for my 60th - have been advised a cocktail dress is needed for July thus year . I am size 10 , 5ft . I want to look classy but not frumpy. Ideas please because I am bored of my normal clothes

Do you want to spend £50, or £500, or …?

Ideally under £275 , I am not looking for fast fashion, ideally something which I can use on again. I don’t need to be super trendy or frumpy