Thanks everyone. Dean - they are still telling me there is no availability at Hilton Head but, the guy today put me on hold and when he came back told me this was the only place anywhere near a beach in America that he could find for July, August or beginning of September, so I am not sure if he was being entirely honest. He also said he couldn't put it on hold, as I already had the Gran Canaria booking but, I think he was fibbing as the girl the other day put Marbella on hold (I decided not to take it as I really didn't want late September).
Maybe I should keep calling. I would really like Hilton Head. I emailed them a few days ago and asked them if they would put me on one of those ongoing searches but, they haven't got back to me.
The details for my original booking in Gran Canaria came today and I definitely want to swap, as there is no oven, just microwave and rings and we like to eat in the rooms quite a bit. European accommodations just don't seem to come up to the same standard as American ones.
To the person who suggested I was wasting my money - I have to say that I couldn't use these points at a Disney resort before August and didn't want to go on a wait list for July at Hilton Head or Vero incase I didn't get lucky. With hindsight, I could have waited and banked my points with II later but, I panicked at the thought of getting nothing and losing my points. I did consider renting but, unfortunately put the points up for rent at the time when the boards crashed for ages, so i did not have any replies until much later, when i had already deposited the points. Anyway, I did worry that if I rented my points out, say for a July ressy, that the renter might back out and I would end up losing them.
Hopefully, some of those rooms will come up at Hilton Head soon anyway, if no Marriott members want them. I know the Marriott and Four Seasons resorts look just as nice as the Disney ones and I will be very happy if I can get a Hilton Head 2 bedroom in August for only 200 points. I think it would have cost me closer to 300 points at Disney's Hilton Head Island Resort.