Edinburgh is great, forget league tables (I didnt know about them falling?) as it has a great reputation and always will regardless of where it is in league tables.
I think the ones you should be aiming for are Bristol, Bath, Cambridge, Durham, Edinburgh, Imperial, St. Andrews, UCL, Warwick, York, etc.
I think those are pretty much the best of the lot for CS in the UK. When I was choosing I made a shortlist of about 20 places and did some research to eliminate as many as possible until I had 4 choices which I was happy with, I then looked for an insurance choice and that was it. When doing your research make sure you consider where it is, i.e. what the city is like. I ended up at Durham because I loved the city more than any of my other choices, it was a tough decision when I had to choose between Bath and Durham though.