Electrical / Battery Fault?

[Mayhaila]

New hydraulics pipe fitted by Citroen garage (Slaters in Abergele). Since coming out of the garage we noticed that a red light appeared on the dashboard (near the passenger side by the hazard warning button) and the interior lights seemed to stay on for about 20 minutes before going off. Everytime any of the electrics were used e.g. indicator there seemed to be a noise coming from the relay unit (fuse box) area and the battery light on the dashboard pulsed in sequence with the indicator click. This noise got louder everytime additional electrics were used e.g. lights, electric windows etc. After a few days came out to the car and realised that central locking didn't work and only drivers door open. Tried to start the car and nothing happened, completely dead!! Thought car needed new batter went to buy one and fitted it. Started up the engine, headlights started flashing on their own, the scrunching noise was still there and the battery light was still pulsing. After checking each and every fuse in the car front headlights stopped flashing, but could still not get central locking to work. Left the car over night and checked car next morning to discover that the brand new battery was completely drained. Any advice would be gratefully received please from you more experienced Citroen XM drivers....... Love the car and don't want to sell it but car is costing a fortune at the moment as it has been in the garage three times for hydraulic pipes to be fitted.