Bonus are a first class outfit. I did my CPL/IR training with them many years ago and they were flexible and friendly. The downside is Cranfield is expensive and Bonus have to pass on the costs for landing etc to you and it starts to get expensive on courses where you are doing a lot of flights like the FI.
I have done all of my Instructor and Examiner courses over the years with Ontrack Aviation at Wellesbourne. They are incredibly flexible, staffed with some of the most knowledgeable guys in the industry and a pleasure to work with. Wellesbourne is also cheap to operate from and this keeps the costs of the whole job down.
However, I would suggest you take heed of comments from people liek tropical fridge. There is no work for FI's at the moment as there is a glut of them kicking around. We are getting dozens of CV's from hopefuls every week at our place.
£7k is a lot of money to spend without a return at the moment......