So to recap
Car had warped discs, 3 faulty abs sensors (3 open circuit zero ohms) and one 1.5 ohms? Do you meam 1500 ohms or 1.5 k ohms? If not that one is faulty too...
Apart from the work you have done, does the braking system look like its been worked on before?
Maybe its been butchered by someone? Has some one attempted a shuttle valve bypass on the abs like what they do on discos...
Sounds like someones been messing trying to get rid of the amigos for mot purposes. ...