If you have the space, then one of the Buddleja davidii types (The Butterfly Bush) will be just right - Black Knight, Empire Blue, Peace, Royal Red, Nahno Blue (shown) and Harlequin are all good ones .   
Buddleja Nahno Blue, Lythrum salicaria, Hebe Midsummer Beauty 
Agastache is very good fro attracting all types of insects. Lavenders - especially the 'angustifolia' types (English) are also good fro bees and butterflies.
Hebes are also great for butterflies. Pyracanthas also for the flowers in early summer, and then the berries for the birds in autumn/winter. Cotoneasters will also fit the bill. (Excuse the pun!) The Spiraea group, Lavenders, Perovskia, Syringa, Viburnum tinus and V. opulus and the summer heathers will all attract a wide range of 'flying' insect - bees and beneficial hover wasps in particular. Some perennials which will attract wildlife, include Achillea, Lythrum, Sedum spectabilis (a must) Scabiosa, Asters (Michaelmas daisies). The perfect annual for this, Phacelia! Most night/evening scented flowers attract beneficial insects! | 