Following is my experience- hope it will of use to anyone.
1. visa expiring in sept 2011
2. PEO app time 1030- arrived at 10:00. Thought wont make it due to morning traffic.
3. @1025, initial check done , given token(queue number).
4. @1030 payment done. IMPORTANT i used NATWEST VISA DEBIT CARD. the finance lady had to call my bank for authorization
and me had to then giv secret word/password. Not sure wt wud have happended in a postal case.
5. @1215 biometrics given. My mistake as initially i went to wrong floor.
6. @1300 biometrics results arrived. Called by case worker.
7. I had submitted with form:
12 month payslips(April 2010- March 2011)- Same employer. Signed and stamped.
Natwest original bank statements (natwest were very prompt in sending me the bank statments with my name,addres, natwest logo
within 2 days).
P60 (as I had shown april -march earning period).
Original degree certificate.
for age (passport)
8. Case worker just asked a few questions, like how many source of earnings- mine was 1. So no issues. Keep it simple

9 . @1430- visa extension approved. June 2011- September 2013. (wich is a bit surprising as i thut sept 2011-sept 2013).
My advise.
- plan properly for the journey esp if croydon. London is a big city-
- ask your bank if any authorization is required beforehand. AVOID any card payments if possible.
- The case worker mainly referred to the salary slips and NOT p60. Which is further proof tax docs should be avoided
as proof of earning. He may have referred to it if I hadn't provided the s-slips though.
- the caseworker initially granted me extension June 2011- Feb 2013- I pointed this out- and he corrected it.so double check
the doc given to you at the end for verification.
- Highlight the salary in bank statements. As cw asked me to do.
- Submit photocopy of all the docs- as cw had to do this.
- for PEO booking, try after 9pm.
- generally i found the staff quite friendly.(contrary to all the posts here).
Good luck.