I had this a few years ago so I completely understand the panicky dread feeling you will be having right now :( all A-OK now though, so I thought I would tell you what happened to me as it might be reassuring:
I was invited to the hospital for colposcopy. This was unpleasant but not painful - think smear-test++ - and the dr and nurse I saw were both the most kind and understanding HCPs I have ever had any contact with, so much so I actually wrote to PALs to pass on the compliment officially. At this appointment I was sat in a dentist type chair with stirrups, speculum inserted and then they had a good look at my cervix whilst painting on various different chemicals. The reaction to those chemicals (colour change etc) highlights any areas of concern. I was allowed to look at this on a TV screen (which fascinated me, but say no if you are squeamish!). From this examination they thought they could see some areas of high grade changes so they did some biopsies - this felt like a big pinch and made me jump but wasn't painful and the lovely nurse held my hand all the way through. I got the results from this back a couple of weeks later, and the biopsies showed only low grade changes. Because of the difference between the examination and biopsy result, they repeated the whole thing a few months later just to double check nothing had been missed. At this appointment everything just showed low grade changes so they were content to leave me on watch-and wait rather than having any treatment. I had one more similar appointment with colposcopy and biopsy a few months later which showed the changes had resolved themselves (apparently this is common with low grade changes) and they were happy to discharge me to my GP. After that I had annual smear tests for three years to make sure everything was staying normal, and now I am back to the usual three-yearly schedule!
So essentially it was an unpleasant and scary few months, but everything has turned out ok! Please do ask any questions if you have them and I would be more than happy to talk a bit more about my experiences. Big hugs and handhold and I hope your hospital appointment comes through soon!