Ouch, Marlene! I've done similar things before! Oleanders grow like weeds in my area, but the southern Arizona climate is far different from the UK. If you can't send them back, try planting them in dark colored plastic or glazed pots, in the hottest, sunniest part of your garden--say, against a south-facing stone wall--and be ready to bring them in to a sunny window in winter. A high phosphate and potash feed, such as tomorite, might help with blooming, also.