Southampton has essentially no parking, especially if you want to stay overnight.
I suppose the LOS development means B&N will move out of Bembridge so the airfield will have to stand on its own two feet. I can't see why it cannot. In the many times I have been there I never saw a single B&N movement, so while obviously there are some they cannot amount to a majority of movements.
Bembridge may go AFIS, especially as it has no (published) IAP.