naturalisation application - residence

"Hi! I am an Australian citizen with Certificate of Entitlement to Right of Abode and am planning on applying for naturalisation next month. However, I have some questions about proving the residence requirements.
Firstly, since my passport is not stamped when I enter the UK (except for initial stamp 21/7/03) I have to provide letters from employers, government agencies proving that I was resident fo the time (BIA Guide p 27). I can do this for the period from beginning November 2003, but cannot get letters for earlier period as I was absent 25/7/03 to 29/8/03 and after my return was unemployed until the beginning of October. Does it matter? Can this period be counted as part of the the days I can be absent from the UK?
I want to apply at the end of July but now I'm thinking I'll have to wait until later. Is there any other way I can get proof of being in Britain in September/ october 2003?

Secondly, if I do apply on 21 July (since I was physically present then) I only have a window of 4 days for them to receive the application as I left the UK (to get married) on 25 July. Is that enough time for them to receive application - using post not NCS since I live in any area not near a NCS centre ? I know it seems a basic question, but I worry anyway!