Hi the PPl exams and quite hard work but not excessive. I did mine in 6 weeks, while flying full time as well. Works out at 1 exam a week and 1 exam for good measure. I reckon you need to do about 7-10hours work per exam to pass them, really depends on your knowledge already though. The more flying you do the easier some are. Ones like Navigation and Communications are pretty straight forward if you've already done alot of flying by the time you take them. Other's like Airlaw can be pigs.
It is possible and I know people that have done it, to do a week intensive course, 7 days and 7 exams. It seems to work as well..
My recomendation is, Do the Airlaw exam, this has to be done 1st anyway so you can go solo, see how you get on and then judge how long it will take you to complete the rest. Only advice is get them over and done with ASAP so you don't have to worry about them in the run upto your skills test.
Good luck anyway.