When applying for a UK passport fort my 3 year old, it states i have to provide photo evidence and address evidence. Whats the normal thing to submit for this? He has nothing but his birth cert.

Also just to confirm it's ok that his mother and I aren't married isn't it? Cos he was born after 2006?

So it's:

Photos

birth cert

me and hers birth cert

and some photo and adress evidence

Help I'm pannicking and confused!!

Yes, as he was born after 1st July 2006 he is British, even though you and his mother are not married.

Provided

1. you are named as his father on his birth certificate;
2. if he was born outside the UK or a qualifying territory, you are British otherwise than by descent (see here). You will need your long form birth certificate to show this.

As for your other questions, I'm afraid I can't help other than point you to the supporting documents leaflet.