Ultrafine Extreme 400 is rebadged HP5+ from all the reports. Traditional (cube-grain) films are going to be grainy, you can try to fight it by using a developer like Microdol (Mic-X) to soften the grain (or at avoid grain-enhancing developers like Rodinal), or you can switch to a tabular (T-grain) film like Delta or Tmax. Do note that T-grain should be fixed for roughly twice as long as cube-grain.
Personally I think grain is part of the 400-speed film "experience", if you want perfectly smooth grain shoot 100 speed or slower. Acros (T-grain) is practically grainless even in 35mm and subjected to Rodinal.
Ilford does not sell the 'Ilford' emulsions to be re-badged. They have even publicly stated so. If you have the cash, though, they will happily make film for you, but it will not be HP5+ and rebranded.
"Often moments come looking for us". - Robert Frank
"Make good art!" - Neil Gaiman
"...the heart and mind are the true lens of the camera". - Yousuf Karsh