Overall, the phone call from Neville is not a bad idea.
It created several hours of mayhem outside WHF where Sheila apparently had the gun & was still alive, or had killed everyone. Once the raid team enter the house, what do they see ? A dead Sheila with a gun by her !
The police knew nothing about Jeremy. They believed Jeremys father would phone him if Jeremys own sister was going crazy. Why would Jeremy lie ?