OP, this is shit!! I'm so angry on your behalf.
Do you believe the H bar or dropped kerb will actually change anything? If they're parking across your drive now as per the pictures they surely won't be put off by an extended dropped kerb?
Agree with PPs that you need to call police and get a contact (PCSO, Neighbourhood Watch type) who you can liaise with and email directly with details of all their crappy parking.
Wish we knew where you were - OH is also fucked off on your behalf and said he'd go round there for you. He's a scary guy when he wants to be xxx