If you have nothing more than your phospolipids and cholesterol you can use UV spectrophotometry since cholesterol absorbs in the UV. You have to prepare a calibration curve with pure cholesterol in ethanol and then you read the samples. I guess this could work only if you have phospholipids and cholesterol or another substante that absorbs 300nm+.
Phospholipids should absorb in 210 and cholesterol near 230 nm. But I guess you can record a full spectrum and select different wavelenghts that don't overlap.