Just remember going to SFC you have to fly to cranfield for the test and to practice the IR routes....so extra costs.
Atleast you will save by being at cranfield already and actually meeting the examiners on a daily basis as most of them go to bonus for a chat.
I found Bonus really good very friendly and I felt it was more of a family vibe going on there and you will get looked after.
I completed my IR conversion in 20 hours 5 more than the minimums so I was happy.