I have an issue that's been persistent for a couple of months now. My previous car battery occasionally would go flat but would be fine after jumpstart it, few weeks would pass then flat again. Now it's every day. I purchased a brand new battery of the  brand Bosch and started to happen again after a few weeks of use. I had AA even com see if there was a faulty battery but after a check it was just drained. He checked all the lights even boot lights, nothing was found at least that was visible. I now have to take the negative out of the battery so it doesn't drain so I can use it next day or when I go to work. Has anyone had a similar issue that can give me a hint or suggestions on what I can do?

Aftermarket radio?

No, it's the original radio. I had installed a Bluetooth media device but I even tried unplugging it but it still happened 

If you have a Multimeter with an Amps range you could try and measure the drain current. With the bonnet open, the battery negative disconnected and the car all locked up, connect the Multimeter on the Amps range between the battery earth post and the disconnected lead (negative to battery post). This should give you a measure of the drain current. With that information, you would be better placed to find the cause of the drain.

I am assuming that the AA man confirmed that the charging circuit is working as it should.