Get an 18v one for sure no less.
I have this one... http://www.diy.com/nav/fix/power-tools/d...d=11738455
Would recommend checking screwfix aswell they usually have some good deals on. Also Dewalt and Makita are good but more pricey than Bosch. I think!
Edit: Checked for you... http://www.screwfix.com/c/tools/18v-cord...cat2700016
I have this one... http://www.diy.com/nav/fix/power-tools/d...d=11738455
Would recommend checking screwfix aswell they usually have some good deals on. Also Dewalt and Makita are good but more pricey than Bosch. I think!
Edit: Checked for you... http://www.screwfix.com/c/tools/18v-cord...cat2700016
Doesnt even own a 306.