Garmin watch battery

Hi everyone, this might be an absolute DUNCE of a question but I'm struggling to find the answer! I've borrowed my brother's Garmin watch and footpod (he bought it new last year off the internet) and he told me the only thing needed was a new battery for the watch as it was dead. Cannot for the life of me find out where to get this battery from and I'd really like to use it for the last 6 weeks before the marathon - am based in London so if anyone knows then please let me know!!

Try this:

http://www.garmin.com/uk/support

I an waiting for my Forerunner 610 to turn up.  What does the foot pod do?

It records your running cadence i.e. how fast you are moving your legs. It can also be used to measure the distance you run if you are indoors on a treadmill or outside where there is no GPS coverage