Soursprout you are very welcome 
I just checked the first GCSE 2018 thread start date and funnily enough, we will be a year old tomorrow. It started with a bit of chat about what preparation, if any, might be done in the Summer holidays and gradually things built up from there.
It took us to December to finish the first thread, but by the first week of exams in mid-May we were going through almost a thread a day.
I can't recommend strongly enough trying to create a group like this. It's very unlike almost every other mumsnet thread. Sniping is frowned upon (so no AIBU for a start!) and somehow we manage to celebrate success without pushing down on anyone else. When someone needs support, they get it. Basically, decency prevails. These threads made this last year infinitely easier for me, and I can think of lots of times it has helped me to help DS.
So, yes start a thread now. It's a very good idea!