I think not all the UK servers are actually located in the UK or at least close by. I seem to notice quite a big difference between them at times too, whether that's an issue with their connection, their location or something else noone can know.
The only thing I can recommend is that you try playing CF at a friend's house or something to see whether the problem is even related to you or if everyone there has the same lag issues.
If you want to generally "boost" your connection just kill as many apps that download/upload stuff (try something like Smartclose or Gamebooster), but I doubt that would help if your UK3 / UK4 ping is acceptable :S