Ultimarc is based in the UK allright, but I think it is just one guy, not like a big huge company. Both of them are actually resellers for the sticks. I believe the Ultimarc sticks come from a Japanese manufacturer, and the happ sticks mostly come from a manufacturer in Spain.
As far as buttons go. I have all sorts of different makes, models, and brands of buttons between my various games, and the ONLY difference you can notice is that microswitch buttons make a click when you press them and leaf switch buttons don't.
I personally prefer old Wico joysticks over every other kind, I think they have the best feel, and they don't go click, click, clickety click.