And welcome to the same boat :-) I had a similar result (mine was borderline and high risk HPV) and my colposcopy was scheduled about 2 weeks later, but due to work commitments I moved it to last Friday. They didn't seem at all bothered about the idea of delaying it. I wonder whether they have perhaps just got a free appointment and are hoping you'll take it? I'd ring the hospital and ask why they 'thought it necessary' if I were you, although I really doubt it's anything sinister.
You're quite right, mild level does not normally elicit too much of a sense of urgency.
Remember that the smear is a small sample of cells, hence the colposcopy, at which the doc will be able to see exactly what is going on. If she sees any areas that look like they might be affected by cell changes, she'll probably take a biopsy, which gives a much clearer picture. This is what happened in my case, and I am now awaiting biopsy results, which will determine the next step. If it's mild, they will go for a "wait and see" approach, as these often sort themselves out. If it turns out to be moderate, I will be back for a LLETZ procedure to remove the abnormal cells.
If you are at all concerned or fearful about the colposcopy, please read my post "Scared Ladies - Please read" as I have described in detail what happens at the appointment and honestly, it really isn't bad. Just like a slightly longer smear test and no more uncomfortable.
Good luck, and here's hoping you get the "move along now, nothing to see here" result :-)