We are in sort of the same situation . . . our landlord is selling our townhouse. BUT he's going through a realtor to sell so she makes all the arrangements. We agreed in advance that we had to have 24 hours notice to show the townhouse and she HAS to be present when it's being shown.

Not sure if there's anything you can do about them just coming whenever . . . our neighbors aren't as considerate as we are and our landlord just lets them in when he's gone.

Good luck . . . I'd just try to grin & bear it until you can get out of there!