Just got a new high capacity (3500mAh) battery and it seems to work very well extending the life of the phone. The standard 1500mAh battery barely lasts a day in the handset especially if its used for Sat Nav or as a video player.

The new battery was a bargain at £9.99 from an Amazon merchant and comes with a new rear case cover to accommodate the thickness of the high capacity battery. Makes the phone a bit heavier and thicker but I think thats a small price to pay for all the extra hours the phone can be used.