List of World Observatories
For a full list of world astro observatories we would suggest looking at this Wikipedia page. The wikipedia list also categories the observatories so that you can tell what they are used for.
Observatories in England and the UK
A lot of astronomy clubs and societies have their own observatories at dark sites. If you are interested in larger observatories used by professional astronomers please view the list of observatories in England.
Astronomical Observatories in England and the UK
If we have missed any out please let us know.
Other Resources for finding Observatories
You may like to try the following resources when looking for astronomical observatories