Hi Ramshorn,
I shouldn't panic too much about when you finish the course before you go to BGS. As long as they have received all of your progress before you attend the brush-up is the main point. I actually only got the last frame completed on the Friday before I attended the brush-up so was in the similar situation to how you plan to be. This was mostly my own fault though as I had found it harder to start studying again than I thought so was playing catch up from day 1!
I would say that as long as you have covered all the learning the material reasonably thoroughly before you go down to Cheddar you should be fine.
The two weeks there is very intense but all the instructors are brilliant. Do your best to get through all the feedback they give you, it is difficult though as there is so much but it will get you good results. It worked for me, 7 out of 8 on the first attempt, only just missed Met by a couple of percent.
I will be back in Cheddar in September as well, but will be on the Mod 2 course.
Good luck with the rest of your studying,
MD2K