Kia cat, I had an MRI scan a couple of weeks ago and like you, was dreading it.
They gave me earphones to wear and I chose to listen to Ken Bruce. I put on an eye mask and they gave me a 'panic' button to hold throughout the scan. The tube is open at both ends, so no one is going to close you in there. They talked to me through the earphones and told me what they were doing. They were very reassuring.
All in all, it wasn't half as bad as I expected it to be.