Hi Guy's,   I went through the Visa Application over the last few months. If you follow everything that Just You tell you to do in the Visa Application  package it is not a problem. 
I too got there at 12:15 for a 13:00 appointment but they dis the first bit at the desk straight away and then just gave me a ticket for my 13:00 appointment.
I too had my Passport returned by post, they provide a 'Grey secure registered  envelope', it costs you but as you say 'Cheaper than taking the day off work and paying the return Train fare'.  People that had supplied a 'registered trackable envelope were told 'Not suitable, this is better.'  Went on Monday and passport returned on Saturday !! 
Looking forward to see people on 19th September.
Jackie 😃