A 300-acre Unesco World Heritage Site beside the Thames, Kew is one of the world's top botanic gardens.
Take your pick from a number of spaces, from the elegant, intimate former royal residence Cambridge Cottage, to glasshouses such as the Princess of Wales Conservatory, home to a collection of rare orchids (that should ease the flower budget).
Whatever you choose, your guests have access to the gardens for the day.
Ceremony capacity: 200; Countryside setting
Royal Botanic Gardens; 020 8332 5641; www.kew.org