This worked and my model is now ready to be sent in for a mould to be made
Welcome to the forum.
I am running 2011 SP 3.0 and did not experience what you described. Unless I missed something.
When I imported the iges file it looked like this
When I opened the other part as well I did not see any gaps as well. But it looked nothing
like Satish's image. Mine looked like an elongated block.
I am attaching the file I created from the iges. Hope it helps you.