As you live in Slough, have you thought of trying for the Slough grammars as well as the test is different?
If you don't like your local secondary, you can put other schools on your list. For example, last year, the Chalfonts Community College took out-of-catchment children from quite a distance , and it has a very good reputation.
Here's a link to the Bucks allocation profile as it is now after the first round of allocation. The areas where a place are offered will INCREASE in the next few month, and the profile will be updated before next September.
http://www.buckscc.gov.uk/bcc/get/asset ... y_2007.pdf
The Bucks CC site aslo has maps of secondary schools and their catchment.
If you want to find out more about schools, you can look at the dfes league tables
and ofsted reports
http://www.ofsted.gov.uk/portal/site/In ... 92a8c0RCRD