HTC has already started rolling out the Android 4.3 update for the One in the United States and Canada. The update brought the latest version of Jelly Bean with Sense 5 and included minor new enhancements and additions.
Now, for the impatient One owners in the European region, HTC UK has provided an estimate of 3 to 5 weeks for the update to land.
— HTC UK (@HTC_UK) October 21, 2013
Their wait will, however, be rewarded with Sense 5.5, instead of Sense 5, that includes quite a lot of new features including customizable quick tiles, updated camera and Gallery app, and much more.
If 3 to 5 weeks is still too much for you, an Android 4.3 firmware with Sense 5.5 for the One is already available for flashing manually.