To give the short answer, the “gh” is the same as the “ch” in “loch,” probably like Klingon. Some Brits use an “f” instead. The “true way”, either in standard dutch or what Vincent might’ve spoken, the answer is more tricky.
The Sovereign.
I was down south and I heard some funk with some main ingredients like the Doobie Brothers, Blue Magic, David Bowie. It was cool.
Cast their vote for “Booie.”
My first thought was “rhymes with snowy”, what a stupid question I’ve never heard anything else, most especially not rhymes with ‘Maui’", but after thinking about it, my boyfriend pronounces it somewhere in between. I’ve always put it down to his (English) accent, as opposed to him actually thinking it should rhyme with “Maui”. The weirder thing is he always refers to him as “Dave” Bowie. Is this a common thing in the UK? I’ve never heard him referred to professionaly as “Dave” and I’m fairly certain the boyfriend isn’t on a first name basis with him.
Colin Powell, whose name is pronounced Coe-lynn Pau-ll in the US, has joked at appearances in the UK that over there his name would be pronounced Cah-lin Poe-ll.
His own pronunciation of his name is odd by American standards. Americans only pronounce it that way because he wants them to.
The story about him changing his name because of Davey Jones the Monkee just can’t be true. He was releasing records under the name Bowie from the beginning of 1966, before the Monkees show had ever been aired & before there were Monkees records.
But Davy Jones was already performing on stage and on television before the Monkees existed, so there was scope for confusion. Probably also an Equity rule, but I don’t know.
Davy Jones was a minor celebrity before the The Monkees aired. He had been in the London and Broadway productions of Oliver! (and was nominated for a Tony), appeared on the Ed Sullivan show and a few other TV shows, and (barely) cracked the the Billboard 100 as a solo performer. Besides, the casting of The Monkees would hardly have been a state secret.
He was also afraid of being confused with J’onn J’onnz, the Martian Manhunter.
You can’t be sure of pronunciation 'cause he’s English
You know how “those” people are. They spell it “B-U-C-K-E-T” but pronounce it “Yes, I can assure you it’s pronounced ‘Boo-Kay’.”
Or
It’s spelt Raymond Luxury Yach-t, but it’s pronounced “Throatwobbler Mangrove”
No no, dear chap. “Throatwarbler”, surely? 
It’s a pity David Whatsit’s middle name isn’t Cholmondeley or Featherstonehaugh.
For a name chosen to avoid confusion with Davy Jones, it has certainly managed to produce enough confusion of its own. Of all the knives in the world …
Why not David Dagger, or David Dirk or David Stiletto? David Swiss-Knife-With-Many-Useful-Bits? But NOT, of course, David Sgian Dubh, or I think the S.D.M.B. would have to start again with the pronunciation thing.
Per wiki
Also, it’s only the Colin part that’s odd by American standards, the Powell part, no American would say Powell as “poe ll” or whatever.
I pronounce it “coolest guy EVER”
I say “Boh (w)ee” [del]but I know it’s really “Bough wee.”[/del] 
For a while I thought it was “Boo ee” like Jim Bowie.
Alternatively, “Jones.”
Here David seems pretty cool with whatever. Recommends “Evans.”
And I went through exactly the same thing as the OP. I suppose “Zowie (rhymes with Maui) Bowie (rhymes with Zoe)” is like Moon Bloodgood’s name [del](which, as far as I know, is pronounced Mudd Bleurdgewd)[/del] in a small way.
Most frequently Snowy, occasionally Snoowy, never heard Maui ever.