So sorry this is happening to your family. 

I don't know if this helps, but my Mum has just had the same diagnosis.  She was seen by a surgeon  in Romford.  .  My understanding is that they are a specialist hospital for brain tumors (I'm making an assumption this is on your son's brain, it can apparently be spinal too).  May be worth contacting them anyway?  

I'm sorry I can't suggest anything else, but hope you manage to find someone who can help you find the answers you need.