Flat battery overnight

Peugeot 106 P Reg has just had a new battery fitted a couple of weeks ago. Battery is going flat every 3 days or so. When jump started it starts up straight away. Took to a garage and had electrician look over it, said the battery was fine and the Alternator was charging the battery. Did all the initial checks and couldnt find the fault. Disconnected the light in the boot as this was staying on. Have had a few problems with signal lights on the dashboard coming on and off (ie Handbrake, Airbag) randomly, dont know if this could be the cause. Any help or advice would be fantastic.

Thanks

Jonny