I may be wrong but have hazy memory of seeing a variety of new sweet potato that you could grow in UK in seed catalogue-thus implying that generally you couldnt.
You are in Scotland arent you? might be bit nippy for them
May be talking rubbish-will check!
Sweet potatoes require a warm, sheltered garden if they are to be grown outdoors in this country. Choose a sunny spot with a fertile, well-drained soil and then cover the area in April with black polythene this will help to warm the ground and eliminate future weed growth.
In May, pot up slips (rooted cuttings) of a suitable variety, such as Beauregard, into 3in containers and keep them on a well-lit windowsill. In early June, these should be planted 12in apart through small holes cut into the polythene. Keep the plants well watered and give them a liquid feed every fortnight. The roots should be lifted in mid-autumn and stored in a warm spot indoors. Slips are available from Thompson & Morgan (01473 695 225, www.thompson-morgan.com ).