It seems that IG withdrawal system is very robust.
I had some withdrawn amount. It is nearly 10 days but has not hit my account yet. I did have another transaction which I did not realize that it has not come to my account either. My Bank says, they have no access tracing the amounts. IG told me that they do not have full control and working on it without giving me a deadline.
With my experience, please always check if you have received the amount in your account and do not just assume that it has been deposited.
Trust, some one higher up is listening it.