nmap <leader>s :%s:\(\_^\\|[ („]\)\([aAiIoOuUwWzZ]\) :\1\2<Char-0xa0>:g<CR>
nmap <leader>s :%s:\(\_^\\|[ („]\)\([aiouwz]\)\s:\1\2<Char-0xa0>:ig<CR>

Refs