The Sand Sculpture Demonstration caters for the short weekend festivals where the emphasis is on a fun speedy sculpture to entertain crowds.  People will be able to see the entire process in a day or two.  If you want to keep the sculptures after the festival then they can be protected and will last a considerable length of time.  Sand sculpture demonstrations start at £1,100.

If you have a good beach then Sand Drawings may be worth a peek. 

You can combine this with a Sand Sculpture Workshop to round off the event.  For a monolithic sculpture that will last months, have a look at Sand Sculpture Exhibition.