I also did the IR part time. If you can take the time off and do it full time instead I would certainly recommend that.
In my situation I managed to get the money together to pay for the course (based on minimum hours) and I had only 3 months before my ATPLs expired (Had the CPL already off course).
With a full time job in biophysics and teaching I had no choice but to IR part time. I quite like my job and I wasn't prepared to walk away from it.
I would go into work early, finish in the evening, cycle to the airport (us scientist guys can't afford cars... especially the scientists that fly), do an IR lesson, have a break, study and then sleep. I think on my most active week I managed eight lessons. Free time simply didn't exist... it was all worky worky and IR.
After three months I was ready. With 48hrs remaining until my ATPLs were about to expire I did the exam. One could say that there was certainly a little pressure on me at this point. With one shot and no chance to fail it made everything rather exciting. Add to all that excitement some nice real IR weather and off I went. Much to my relief I passed the exam (pew!).
If you are working the days and flying the evenings it can get quite tiring (I also had the missus to keep happy). I found that with my time limits etc it took a lot of focus and generally a sheer will that I wasn't going to fail. I didn't have time to take one step forward and two back...
Anyway after all this I got rather drunk and slept for about two days.
Best of luck if you you take this route!