Your homestudy agency is not doing their job. They should know what to do in the US at least! We had to get child abuse clearance, but only from the current county in which we live. (sounds like that has changed) Our HS agency gave us a form to fill out and sign, then sent it to our county DFACS office. (Dept. of Family and Children Services)
This is one area you need to stay on top of. We had one of our paperwork delays because of DFACS.
They are overworked and underpaid. Both times we adopted I ended having to call the DFACS office multiple times to get the paperwork done. I'm sorry you have to deal with so many offices on this. Dealing with one was a pain!
As far as for England, I second what someone earlier said and start with the Embassy. I would think it would be the US Embassy in England????
Good Luck!!
Rhonda