Simon,
Good luck with it, I was one year younger than you when I did the same. Try and balance working through all the notes you will get to learn the material, with some time looking at question banks etc, so you can get a feel for how the questions are asked and dont be afraid of asking around for what types of questions come up most often.
I have a management type job like you, but I'm "lucky" as my daughter swim trains early in the mornings, so I found I had plenty of time at the pool. I found time to do about 2 hours a day for 4 days a week and got through it in 6 months. That was about 4 yrs ago. I also found the time to do the CPL flying course and the FI rating since then and I'm now happily doing some instruction on weekends and some summer evenings. I'm currently going through the short course to enable me to teach IMC.
If you want to learn it you will find the time to.
Which distance school have you signed up with?