So much of a muddle of non-evidence to wade through. That's what replying to this post has made me realise!
Ok, here goes. In my understanding....
Your first paragraph has not, and will not, be covered, because he didn't do it.
Phone numbers hitting off masts wouldn't give us any more information than we readily have, because we know where everybody was and at what times, this is not disputed.
A forensic botanist, Dr Mark Spencer, has given evidence. Google for details.
Apparently, in his first interview, the accused answered 'no comment' throughout. In the second interview, he produced a prepared statement which introduced the third party.
Opportunities to gather evidence at an earlier opportunity were definitely missed. Members of the public had concerns which they reported to the police, and those concerns were ruled out to be unrelated. The most obvious being that a member of the public saw the wheelie bin in-situ at the cemetery, an officer responded and said it wasn't important and authorised its removal to a storage facility. Lindsay's body was hidden 6 metres away. How much difference this will have made, we'll never know