HTC has announced that the One M8 units in the UK will start receiving the Android 6.0 update in the next 48 hours. The announcement came in the form of a tweet sent out by the company's official UK twitter account. Great news! We'll be rolling out the Marshmallow update for the HTC One M8 over the next 48 hours. One M9 to follow shortly. HTC UK (@HTC_UK) January 18, 2016 In addition, the Taiwanese company also revealed that the update will be rolled out to the One M9 units in the country shortly thereafter, although no specific timeframe was mentioned. While there's currently no official word on it, it'd be safe to assume that the update in question will only be rolled out to unlocked units of these devices, with operator-specific versions getting it later. For those who aren't already aware, the Canadian carrier variants of the One M9 are set to receive the Android 6.0 Marshmallow update...
Source: http://www.gsmarena.com/marshmallow_update_for_htc_one_m8_units_in_uk_to_begin_rolling_in_next_48_hours_one_m9_to_follow_sho-news-16142.php