Want to withdraw from my insurance (unconditional) but keep firm.

Hello, I have chosen my firm and insurance options for university this September, with my firm being where I really want to go.

However, I don't think I have achieved the grades for my firm,and I really do not want to go to my insurance choice and would instead prefer to go into clearing on results day if the worst occurs. The problem I see with this is that my insurance is an unconditional.

I know I need to ring up my insurance and ask them to take away my offer, but I've read around and people say you have to be very specific with what you say (e.g. not saying release or something). I just wanted advice on how to deal with this as I'd rather get it out the way now than have to wait a long time on results day.

Thank you