So, don't want to count my chickens, but I might get treated at the Royal Marsden after all.
Yesterday I called to say 'thanks but no thanks' to my appointment on 29th February and told the woman in appointments how unhappy I was about how my case had been handled. She apologised and expressed her surprise and said that she would look into things for me to see if it was still worth me coming in.
I then received a call from the Consultant's secretary (the one I had previously dealt with) who, after some to-ing and fro-ing and inital frostiness, I think realised that there had indeed been an administrative cock-up. She was then enormously helpful!
As a result, I've now heard from the Registrar. Ideally, they would like a patient to have all their treatment - i.e. chemotherapy, surgery etc. - at the same hospital but it is possible for me to have my chemo at Charing Cross and then go to Royal Marsden for my operation. So she is re-scheduling my appointment to see the Consultant Surgeon to May after my fourth course of chemo.
Clearly, I'm delighted. And goes to show that being direct and honest about how you feel, does pay off!