Morning guys,
As I have previously posted, I too was having this problem, so I took it into the Apple store at Meadowhall, sheffield, on sunday.
I explained the problem I was having and, although he didn't tell me specifically what it was, his reaction gave me the impression that I wasn't the first person to come in with this problem.
As soon as I explained all 3 symptoms (no audio on video recordings, no speaker phone and no facetime audio) and told him a restore had done nothing to helped, he offered me a new handset.
He nipped into the back, brought out a black box containing the new phone, activated it, got me to sign some forms and I was done. Whole process took no more than 10 minutes (plus an additional 40 waiting to actually see someone!). New handset works great!
So if you are having this problem, I urge you to take it into your nearest apple store. Chances are you will get a new handset out of it.