2003 Rover 75 Water in fuel tank

Engine Mechanical problem
2003 Rover 75 Two Wheel Drive Manual 53000 miles

Hi,

Had problems starting car, turning over but not starting. Breakdown recovery thought it was fuel pump. Towed car to garage bought from 7 weeks earlier with 3 month warranty. They changed fuel pump, no joy, had auto electrician looking at car, no faults found. 2 weeks later garage said high level of water in fuel tank. They don't know what to do next. I've read that if they drain off contaminated fuel, refill, change fuel filter, should be ok. Is this right? All suggestions welcome.