Sounds like a drain is present.  Gadgets - radio, alarm, remote locking
etc.. all draw a small amount which can flatten a battery over time.  
However, if this is a new problem, I'd get an auto electrician to check for
problems, possibly with the charging circuit.

Once a lead-acid battery has been flattened, if it's left like that for a
while, the plates can sulphate, and the battery capacity is reduced.

Good luck,
Andy

Thanks for the help Andy.

Never asked a specified auto electrician to check before - always brought it in to the garage and they'd just look at the battery.

keep u posted