[U],
By all means do intensive groundschool courses, particularly if time is of the essence for you, but my opinion / advice would be to read and re-read the Thom or Pratt books. It will probably be quite a bit cheaper.
Think also about how well you will remember information that you have "crammed" for the purpose of the exam.
After the first reading do the relevant exam in the PPL confuser, then after the second time do the exam again - see where you are getting things wrong twice, revise those topics (hopefully very few) and sit the exams.
Worked very well for me.
The only ground school that I did (and thought was money well spent) was on R/T.
Good luck.
SD
ps - please don't think I am against anyone who provides such courses!