YANBU -- I felt much the same before I had DS, he was 10 days late but my mum and stepdad insisted on coming over a week before his due date, I was really worried about her invading our space.
However... as it happens, as soon as DS was born I wanted them to see him, they held him on the day he was born (in hospital) and it was a special moment for all of us. They also helped with cooking and cleaning, and holding the baby so DH and I could catch up on some much-needed sleep. In the end I did really appreciate having them around. Not to say that you'll feel like this!
Then again I am close to my mum, although she can bug the hell out of me, at least she is reasonably good at taking a hint to clear off for a while