1. as others have said you need to apply for ilr, maybe flr but i doubt it (see next answer)
2. earliest you can apply is 27/9/09 + 2yrs - upto 28 days = as you've said 30th aug 2011, latest the day your visa expires 28/8/11 ( but i wouldn't leave it that late)
but have you noticed the earliest you can apply is 30th aug, yet your visa expired on the 28th ...
you've the old 24 months, you must have been one of the last to get a 24 month one ,,they are 27 months because of this reason.
anyway thats why i said you might want to apply for flr (not worth it for 2 days thou )
you need to apply b4 your visa expires so you cant apply on the 30th, the 28th the day your visa expires is a sunday !,
i would apply on the 25th a Thursday, got to the post office and use next day special delivery and keep the receipt.so shouldnt have a problem applying a few days early, your more likely to have a problem applying after your visa has expired.. thou probably no risk of it being refused for a day or so,
or you could leave it til friday 26th and get Guaranteed Saturday Delivery on the 27th, thats the latest you could apply
but better to be safe that sorry, i would apply a days earlier than days late..
you might have problems using a peo because of the dates when you can apply, i'd probably use the post and post it on the 25th using next day spec del so they have got it friday.. the 26th
3. probably a month or so..
if your a bit worried about what i've said, should be no need to be, phone the UKBA helpline see what they advise..