Hi Vegas, I've had this done and it wasn't as bad as I was expecting! It was uncomfortable but wasn't painful. They didn't find anything on mine, so not sure if this would have affected the pain level. There was a little bit of waiting around. I was called through and put in a cubicle where the nurse went through everything with me, gave me my antibiotics and got me into my gown. Then when they were ready for me we walked to the treatment room. They were really nice and put you at ease. The actual proceedure didn't last long and then you were free to go.
Good luck with it! x