Car wont start

Hi,

My BMW 120D has been parked up for two years as I had to go away to study. I used to start it once or twice a month throughout this period. Sometimes the battery used to be flat and when I would go to turn the car on it would make a clicking noise. But then I would charge it and it used to start again.
About 2 months ago it looked like a rat or something had got under the bonnet as the sponge lining the bonnet had been nibbled at slightly. I put in some rat poison and charged my car up which would start properly (no weird noises either) There didn't seem to be anymore rats as they aren't taking the rat poison from the car anymore. And my car was started up successfully over the next two months about twice a month.
The other day, I went to start my car and again the clicking noise came, I charged it for a full day and even tried jump starting with another car but now all I get is the noise a car makes when its about to turn on, except it doesn't turn on. The battery light still shows as green on the battery so I'm just wondering if anyone knows what could be up.

Any advice would be much appreciated.

Thanks a lot,

Poonam.