Here's my twopenneth worth:
Definitely get those exams out of the way as soon as you can. But, be positive. As has been said already, it is possible to get some lovely flying days in the winter.
I had my first lesson on 3rd October 2009. I passed my Skills Test on 24th April 2010. So it can be done. OK, I was able to be a little more flexible than you with times, but I quickly learnt to book way more lessons than I needed, knowing that a fair few would be cancelled. If they weren't, then
I cancelled them instead if I thought I was getting 'overloaded'. I would suggest that if you are able, you pre-book the days and times you can do
now for the next four weeks and keep this rolling week by week.
Congratulations on your progress so far, and fingers crossed for lovely winter weekends for all of us......