Currently Apple's US website says that the Apple Watch is due in 'early 2015' - with the UK website saying 'in 2015'. While discussing Apple's Q1 2015 financial results with analysts last night, CEO Tim Cook said that it would be was "on schedule" and will ship in April. The company reportedly hasn't publicly committed to a date because Cook and co. are still working on the device's battery life.
I contacted Apple to see if this April date is for the UK too, and was told "We haven't announced which countries will launch in April yet" by an Apple spokesperson.
So the Apple Watch might be here in April, it might not. If you were to wilfully misinterpret what Apple's spokesperson said, you could say that the company hasn't even confirmed that it's shipping the Apple Watch in the US in April. Maybe it'll ship in Japan-only first. Or Azerbaijan.
However, based on common sense and Apple's previous release behaviour, we'd expect the Apple Watch to ship in the US first, so if you're chomping at the bit to get your hands on one to test apps you're developing for it on - or just to play with - you might need to book a transatlantic flight in April.