I studied for my A-Levles and did my PPL at the same time - and in the long term regretted it.
I found it was a great stress releif, and provided an excellent change from studying - but, I firmly belive that I would have performed better in my exams if I wasn't being so focused on my flying. I spent more time in the liberary thinking through my down wind checks when I should have been doing A Level statistics.
As for A-Levels are that much work - looking back, they wern't. Looking back I could plan better and probably perform better -but at the time they were the hardest exams possible.
I got good grades, but could/should have got betters. Its sad case of society but 7 years on, undergraduate and postgrade degrees later and applying for a job recently I got rejected on the basis of my A-Levels.
You have a long time to learn to fly. Put it on hold for a couple of months, but keep saving the cash as if you were flying. Then when you are done, go and do and intensive week with the money you have saved up. THis will be more productive than once a week as you will not need to keep refreshing - plus you get a week of flying which is immense.
In summary - there is no right and wrong answer,
but hope that the comments from the other guys, and mine - help you make a good decsion.
Thanks - FW