Dahlias, gladioli, sweet peas, larkspur, lisianthus, statice, helichrysum, gypsophylla, stocks,

That's off the top of my head

Calendula ...With this flower at least you could use the petals in salads.....Scabious which attracts butterflies and bees

what about chrysanths, rudbeckia and sunflowers to add to those already mentioned.

Providing your soil conditions are right, you can grow the same cut flowers on your allotment as you grow in your garden, only instead of growing them in clumps, grow them in rows and treat them as a crop, Derek.