Do I have to accept Insurance offer

What you read is right - they have to agree to release you into Clearing. You obviously don't have to go there - nobody can force you to - but nor do they have to release you (although they have nothing to gain by being obstructive, so I imagine they would). There is a useful guide here on TSR, and the subheading If you change your mind about your firm or insurance covers exactly your scenario.

Ahh okay thanks a lot, how long does getting them to release you actually take? As in would it be worth calling them and asking tomorrow or waiting until results day?

I'm not 100% sure how long it would take, but I have heard that it doesn't always happen immediately (as in, it could take a few days). If I were you, I'd phone your insurance tomorrow and bring up the possibility with them, as they'll be able to advise you about what you and they can do.

I decided a while back that I don't in fact want to go to my insurance and would rather go through clearing, if it comes to that, however is there a way of rejecting my insurance on results day or am I obliged to go there? I read someone say that you have to ring them up and ask to be released? Any answers would be helpful..

Ahh okay thanks a lot I'll give them a ring tomorrow then