Explorer has stopped....

[GRANDDUC]

Appreciate some advice as my 2006 Explorer has stopped after my usual manual wind failed to get it going. As I only wear it occasionally it's become normal practice to manually wind -around 20 crown turns- and off it goes however, when I did this recently there was much less resistance and the second hand didn't move. I gave it a few shakes and noticed the second hand moved forward a few seconds then stopped and vibrated back and forth before completely stopping. I've owned it from new and have never had it serviced. Clearly something has malfunctioned/broken. Can anyone recommend a London based independent watch specialist as I would like to avoid sending to Rolex as no doubt it will cost considerably more.

Thanks in advance