I'm sorry to read of your diagnosis and I hope you are responding well to treatment.
In answer to your question, unless you are unhappy with the treatment you are receiving from your hospital and clinical team, or your are running out of conventional treatments, there is no real advantage to being refered to the Marsden, though there is nothing to stop you asking for a referal. Do you have any special reason for wishing a referal? For my part, I have been treated for liver mets for more than four years now and I am more than happy with my hospitals approach to my treatment and care.
I have been following these posts for a while but rarely post. I was diagnosed with secondary mets in my liver, bones and probably my ovaries in August. I have been told by a friend to ask to be refered to the Royal Marsden. I was wondering if anyone had done this? And how they got on.