The closing date for Slough 11+ applications are usually at the beginning of october, so no problem with this.
Look here viewtopic.php?t=2707
for information on admissions, and on the school websites:
Langley Grammar http://www.langley-grammar.slough.sch.u ... ssions.htm
Herschel Grammar http://herschel.slough.digitalbrain.com ... page/home/
St Bernard's Catholic Grammar School http://www.st-bernards.slough.sch.uk/
Slough Grammar (Info out of date on their site. Haven't updated it for this year 11+)
Have you started preparing your daughter for the tests?
Best of luck