The 11+ is not a single national exam. Different counties and cities run their own versions, and the rules vary noticeably. Here's a quick tour.
Kent
The Kent Test is a single test taken in early September, covering English, Maths and Reasoning. It's GL-based and famously high-stakes — Kent retains the most grammar schools of any English county.
Birmingham & the West Midlands
A consortium of grammar schools uses a shared CEM-style entrance test. Vocabulary range is broad, and timings are tight. Practice now in mixed mode if you're targeting a CEM-style paper.
London
London has very few state grammar schools but a huge density of selective independent schools. Each writes its own paper, though many follow an ISEB or "common entrance" template.
Other counties
Buckinghamshire, Trafford, Lincolnshire and many others all maintain grammar schools with their own variants. Always check your local council's website for the definitive format.