Whatever the style or situation, there are summer container plants to suit;
Focal point: Argyranthemum (marguerite) grown as standards, dahlia, fuchsia, Lantana, lavender, Phormium and salvia.
Upright (larger): Ageratum, Brachyscome iberidifolia (swan river daisy), Diascia, heliotrope, Lantana, marguerite, Osteospermum, Pelargonium, salvia, Verbena, Zinnia.
Trailing: Calibrachoa (million bells), ivy-leaved pelargoniums, lobelia (Lobelia erinus Cascade Series), petunia (Surfinia types) and Verbena (trailing).
Light shade: Begonia, Glechoma hederacea 'Variegata' (ground ivy), Impatiens walleriana (busy Lizzies), Lysimachia nummularia 'Aurea' (creeping Jenny), Mimulus Magic Series (monkey flower), Solenostemon scutellaroides (coleus), Chaenostoma cordatum 'Snowflake' (Bacopa), Torenia.
Drought tolerant: Aeonium 'Zwartkop', Echeveria, Mesembryanthemum, sedum.
Foliage: Coleus, Dichondra 'Silver Falls', Helichrysum petiolare, Senecio.
Scented: heliotrope, Lobularia maritima (alyssum), Matthiola (stocks), Nemesia, Nicotiana (tobacco plant).
Hot tropical: Begonia (tuberous), Bidens, Canna, Coleus, Gazania, Lantana, Tagetes (French and African marigolds).
Cool and calm: Alyssum, French lavender (Lavanula stoechas and L. dentata), Lobelia, marguerite.
Links:
10 AGM perennials for containers
RHS Find a Plant