Dartford Warblers (or lack of...)

Has anybody seen any Dartfords in the north of the county this year??? I see from Rich C photos that they are still doing ok in the south. I spent nearly 5 hours yesterday at a site in the north of the county that I believe was the first confirmed breeding location in 2003 with circa 6 pairs. The weather was perfect and everything was singing except for Dartfords. There was absolutely no sign of any. In the last few weeks I have spent a similar amount of time at two other suitable locations (both of which have previously recorded Dartfords) again with a 100% failure rate. Obviously don't post location details here if you have seen them in the north but I was curious to know if they are still around.