Hi,
as far as I am aware, if the land is considered to be within your own curtilage then you can take off and land all day, every day, to your heart's content without anyone's permission.
If the land is owned by you, but adjacent to your property, then technically you are limited to 28 movements in any one year. (Unless you get specific permission ) However, this limit assumes that someone is counting. i.e. if you were not upsetting anyone and no-one actually complained to the CAA then you are likely to get away with it.
I believe that you are allowed to erect structures that are not considered permanent e.g. a windsock, but a hangar would require planning permission. Likewise, I'm fairly sure that you can spray a letter "H" on your grass, but if you were to construct a helipad then that would need permission. I suspect however that a circular or square shaped patio would be more than acceptable!!!
It may be worth confirming everything I have said, but I'm reasonably confident that it's accurate.