dm me and I'll send you my codes for the online editions if you want?
May I ask what online edition book?
I'm a few days late to this thread. Although its not a great decision to leave stuff like this to the last month, I feel like you can easily get a decent grade. If you manage your time wisely, and do short bursts of intense but effective revision, you'll be fine.
What I did for my GCSEs was study a certain topic, and find exam styled questions based on that topic. And then in the last few weeks, just did all the past papers I could find. You'll likely realise that a lot of the exam papers for a subject will be laid out very similar to each other.