Battery draining rapidly

Had engine warning light come on then power steering very stiff. All ABS etc came on then car stopped. Towed to garage by breakdown who said needs new alternator. Got new alternator, warning light stayed on - steering still stiff. Garage then told me the battery was draining and I needed new battery - got new battery drove home. Next day battery dead. Charged over night worked next morning then totally dead the next morning. Now fully charging battery and it is draining totally within 6 hours. Fiat garage said needs alternator (it is brand new - less than 2 weeks old). Need to sort out major battery drain urgently - help please