UPDATE: Went to CW yesterday. Had an online appointment for 15.00. Finished updating bank book bank letter and a statement for January as my 12-month statement only went to 17/01. I therefore arrived at the Immigration office at just after 14.00. On checking my docs (the first cubicle in section L) the very nice IO handed me back the photocopies of my passport as I had copied every page and interestingly the statement for January. The interesting part was she consulted with her colleague and then asked me whether I had come alone, to which I replied yes. She then followed-up with saying "but last year you came with someone?" I said yes that last year I had someone to help me but that this year I was doing it by myself. I was thinking that might be the point where I was going to be told to go back to the agent but thankfully not. So, my docs were handed back and I waited outside L32 which seems dedicated for online appointments in addition to regular ones. No queue number given but at 14.45 a lady popped out and simply said online which was the indication to go in.....so for those using the online booking service you need to listen out for that rather than your name. I then went in to main IO - she took my 90-day report but not my TM30 I had a variety of maps including one hand drawn she took all of them except for the colour one. She spent some time checking my bank statement, I think verifying that I had funds at the time of the last extension and for the few months thereafter. No comment from her about the previous (agent facilitated) extensions. By 15.00 I finished with her and sat down preparing for a long wait. At 15.10 I was called into another cubicle, and I was expecting that maybe at this point they might have told me to deal with by the agent again, but in fact I just signed and my passport was returned with the one-year extension stamped inside it. So, from going into the IO at L32 to getting my passport back was 25 minutes. I was very impressed. It was very busy there yesterday and the online booking was a really useful thing to reduce waiting time. So basically, switching from an agent to self at CW is okay so long as all the paperwork is in order - 90-day reports, TM30 and financials.