I got the same result as you about three and a half weeks ago and had my colp and LLETZ two weeks ago, so you'll see that your timing is very normal. I think the NHS is supposed to see people with high grade results fairly quickly. I wouldn't be alarmed by the speed (in fact, I'd be pleased - less horrible waiting and less time 'til the cells are gone!). That sounds very routine to me.
Some hospitals see and treat in the same appointment (that's what happened to me). Others seem to see people for a colp and then offer LLETZ in a separate appointment. It seems like those who have colp first almost always have biopsies, based on what I have seen here? I imagine they are hoping they'll have the results back for your appointment next week and that will guide treatment? I understand that smears are not always totally representative of what is happening, which is why they do biopsies/check what they have removed during LLETZ. You never know, if your biopsy is CIN1 you might not even need a LLETZ.
In terms of what to expect, your LLETZ will be just like your colp, but rather than having biopsies, you'll have some anaesthetic injected into your cervix and then they'll do the loop, which is very quick and you won't feel it. Afterwards, they use a hot probe to stop the bleeding. Again, you won't feel it. I felt a bit light headed afterwards, but the nurse got me some water and I just took things slowly. My husband was with me (it's nice to take somebody with you). You have some bleeding/discharge afterwards and for up to 4 weeks after. Mine hasn't been that bad.
Hope that reassures you a bit? So many ladies here have been through this process, so any questions, just ask x