Andrew,
I'm in a similar position with just a few more hours logged. I did ATPL groundschool by distance learning taking just about a year to complete it and finished in January. It does take about 15hrs/week to do the study, so impacts on free time if you do it this way. Obviously if you can do a full time course you'll be able to fit it in over the next 12 months while continuing hours building. On completion of all exams you'll have 36 months to gain CPL/IR for them to remain valid. As for the night rating, I don't think it really matters when you do it so long as you meet the criteria of 5hrs night (need to check this myself) before starting the CPL course. I'm doing mine next month as most schools only do this during the winter months ie Nov-March. Hope this helps.
Noz