I think there is little argument that ATC'ers in the UK are amongst the best there are but as a complete service things have got much worse since Swanwick came online. Many routes we fly out of LHR to the North of the UK and Ireland are level capped at FL180 or have to be re-routed at short notice, we suffer long slot delays for many routes and the restriction is more often than not a London one. We are basically unable to operate our schedule a good deal of the time. Add to that the R/T quality from the new centre, which is diabolical much of the time, and all in all Swanwick has not been a a real flop for my point of view.
Many controllers seem to feel the same which means someone should have some very expensive egg on thier faces.