No matter what I do to get my site rank well on Google UK again, nothing happens at all. Why? My site has completely disappeared from google UK but ranks 4th on Google for other countries.
Does your site end with .co.uk? If not it might be wise to change your geographic target group in Google Webmasters Tools.
well that depends on the server you're using and geo you're targeting. I suggest, use the UK friendly sites as your back links. and target local market with Maps and listings.
Building backlinks for UK specific sites may help in this case and also as other members mentioned set the Geo-Target location to UK in your GWT account.