Christine, It depends what your saving for. If your going for to upload to youtube/vimeo etc then go for h264 at a bitrate of 5-8mbps
Thats what those sites recommend.
hampers I was out today following moving Redshanks and its not that hard to be manually focusing with them on the move. Sometimes i was slightly out but could get it back in again quite quickly.
Im sure with practice that sort of thing will become second nature. (hopefully

)
As for the microphone rob bought one and is testing it. I think i might go down the route of an external recorder with a dead cat on the end.
(If i can find one for under 100 quid)