Professional Air Training (PAT) at Bournemouth were very flexible when I did my IR there about four years ago. Briefly, I was running my own business and arranged to travel down to Bournemouth on Thursday evenings (200miles), stayed in B&B, did IR training Fri, Sat, Sun, Mon and drove back home Monday evening and then tried to do five days work at the office during Tuesday, Wednesday and Thursday, again driving 200 miles Thursday evening back to Bournemouth.
I had completely overestimated my abilities to work at this pace for weeks on end and I got very tired.
I really do suggest that the IR needs at least three days a week and you need at least two days a week rest while doing it. In other words full-time with weekends off is good, while part-time i.e. working all week and trying to do the IR at weekends is bad.
This is just my opinion based on my experience, but I did find it exhausting, both mentally and financially.
Finally, Good Luck !