I've seen 5 (1 red, 1 silver, 3 white), possibly a duplicate though so definitely 4, and the local garage said a red one refueled, so 5 maybe 6 in my area. I see loads of Fiat 500 and Toyota Aygo, Citroen C1 and Peugeot 107, so I expect to see loads of ups.
My dealer said they had sold half their years allocation, and that was late March or early April. His problem is getting hold of cars. This assumes he is not giving me blarney, but comments here are consistent with that. Mind you, a garage near Southampton had two available (silver TakeUp and white MoveUp Bluemotion), so I think sales vary. Perhaps everyone wants customised versions.