How do I get my abs light to go out after fitting new abs control unit?

My rover 75 developed an abs brake fault a day after hitting the foot brake pedal hard in a semi flooded road the abs system worked ok, until the fault lit up.Took it to a dealer they put it on their computer and told me the abs ecu was at fault For £850 they could sort it out !!!!!!!!!!!
Took it to a local guy fitted new ecu, still no abs braking and red brake light permanently lit and amber abs light permanently lit? so any idea's please!desperate to get this sorted!

Philip Johnson
February 2010