I see from this story that the UK Met Office is about to give up on its seasonal forecasts. Wha'ever. They're stopping because the forecasts were basically wrong. When it didn't turn out to be a hot summer or a warm winter they came in for a bit of stick. Criticism rarely makes you feel good, but surely they're big enough to take it?
So, rather than work on getting it right, they're just giving up, but I think the PR defeat they've suffered will have further consequences. In addition to giving up the hiding-to-nothing forecasts, my bet is that they'll err even further on the side of caution when it comes to the daily stuff. Expect long range stuff to sound worse that it is, expect METARs to be better than the TAF, well for most of the time anyway.
FWIW, I think the RN does a decent job of weather forecasting followed closely by the RAF.
Edit: It seems (Thanks Tony) that the RAF makes use of UKMO people on their bases, while the RN uses its own forcaster who themselves make use of UKMO data. I still think that military forecasts are better/more accurate, so I'm going to see if there's any data to back up that feeling.