Intermittant starting problems

Car won't turn over hot or cold there is a clicking from the starter motor, Ignition lights fade if ignition key held over after several attempts there will be a series of rapid clicking then the engine will turn and car will start. For the next 10 or so starts the car will be fine then out of the blue back to square 1.
Just fitted a recon starter motor and everything fine for 2 days now fault reappeared battery and alt both checked and ok
Car is a 2002 1.4 petrol zetec with 45,000 on the clock