I am looking to get a spare battery for my soon-to-arrive GF-1. In the past I have always bought third party batteries with good success and would like to the same with the GF-1 to keep costs down. However, I have read of reports of firmware upgrades making third party batteries not work. Does anyone know of 'safe' batteries that work with the GF-1? I'm in the UK so if anyone can point me to UK suppliers that would be great.