Sheila Harrison always looks forward to the descent of the summer visitors onto 'Seafret', her tall brick house right on the front at Blythney, in East Anglia. She loves the way her spare bedrooms are full, from June to September, with successive waves of children - schoolfriends of her own three and the waifs and strays sent by the Country Hosts' Association.But Sheila is not prepared for the uph...