I had the same letter as you about 2 weeks ago.......... it is such a shock, I have never had an abnormal smear until now. You should get an appointment quickly for your Colposcopy, where they can take a look and sometimes they will do the treatment. I had mind last Thursday and had (loop) to remove abnormal cells.
The Coposcopy is not as bad as you think, the local was painful ...... but after that I did not feel a thing. The nurses were lovely and gave me a cuddle at the end. I was told by the doctor at the time that it did not look like cancer and she was happy that she had got all of it.
It has taken 3 days for things to settle down, cramping and bloating after and emosh I am still a bit all over the place.
Hope this helps you.