Yes, I actually made it to St Kilda - one of my personal ambitions fulfilled!
Once I knew I was coming to the Outer Hebrides, I contacted each of the companies that offered trips to the archipelago but they were all fully booked. Luckily, some of them operate extra trips if there is suffcicient demand so I was able to get myself on the reserve list.
After travelling from Berneray (S. Uist) to Leverburg on South Harris and arriving at my hotel, sitting quietly in the lounge having 'afternoon tea' (yes, really!) the receptionist came over to tell me that Kildacruises have been on the phone and there is spcae on tomorrows trip if I wanted it and to be there (Leverburgh) by 07:45.