dropped my Nokia N8 in the bath

If you want to restore the life of the battery you'll need the following (along with the necessary tools):

1.New battery.

2.Toothbrush.

3.Isopropyl Alcohol.

4.Goggles.

5.Nose and mouth mask.

6.Latex/Plastic Gloves.

7.Eraser.

Strip the phone and take out the motherboard. Using gloves and goggles and possibly a mask (Isopropyl is very bad when breathed in especially for your lungs). Dip the toothbrush in Isopropyl Alcohol and clean the board with it taking away all of the corrosion. On the gold contact plates on the board use the eraser to get the dirt/corrosion off them do not use the toothbrush as it could scratch and cause damage. Hopefully if all goes well this should work you may also need to reflow the motherboard to set everything again. There will most probably be parts that need changing but you'll know that when the device is on. After you've cleaned it wait 20-30 minutes for the board to dry (it needs to be completely dry otherwise this could cause damage). Check the board for any black bits that should be gold and try soldering them (if this isn't up your street take it in to a technician). Hope this helps, any questions I'll answer.