Apple Watch lost timer app

Woke up this morning ask my watch to do a countdown only to be told that the timer app is not installed!

The timer app is the only functioning app on the watch since I cannot work out how to make the complications require a long press, they are no good on the watch face; and the only thing I can trust Siri to do is countdown .

The message had a link to the App Store that tried to sell me something with in app purchases!

My obvious concern is why has that app disappeared from my watch… What is wrong with my watch? And how do I get the app back without using the App Store on the watch which is seemingly as bad as the App Store on iOS, all ads and Facebook .