I am the same as you Natalie. I hate interviews and get all nervous and tongue tied. I was made redundant a few years back and was temping whilst looking for a permanent job. I had been to quite a few interviews but not secured anything.
The last interview that I had, I really, really prepared well for it and had someone go through possible questions and answers with me the night before. She kind of made me do a mock interview and she grilled me like a proper interviewer would.
When it came to the actual interview, I found that I wasn't half as nervous as normal and was actually waiting for them to ask certain questions because I knew I had fantastic answers for them! I got the job.
So, you may prepare before hand anyway but get someone to go through it with you (maybe do the mock inteview) and ask them to give you feedback on where they feel you could improve or give a better answer.
Good luck!