Would an Eb whistle be preferable to a D for Jazz/Blues tunes ??
Depends on the keys the other guys are playing in.
An Eb whistle is good for Eb (three flats) and Ab (four flats).
A Bb is good for Bb (two flats) and Eb.
An F whistle is good for F (one flat) and Bb.
A C whistle is good for C and F.
Just depends! If they’re staying mostly in two or three flats a Bb might be your ticket. You’ll probably end up needing to bring several whistles to cover whatever keys they might do.
At work I hear live jazz every day and these guys are nearly always in flat keys, two or three flats is most common. They’re using Bb sax, Bb trumpet, etc. One clarinet guy has told me that he’s not comfortable straying far from Bb, that nearly all the pieces he plays clarinet on are in that key.
Thanks for that Pancel.
I’ve since learned that saxophones are either Eb or Bb so this probably explains why most Jazz stuff is in flat keys as you said.
I’ve had a mess about/improvise with a friends Low Eb and even with my scant Blues/Jazz knowledge it sounds more Bluesy/Jazzy then the Low D I play.
I take on board your advice about a Bb whistle but I prefer the ‘LOW’ end (I dread to think what a Low Bb is like)
OK, before i say all this, please bear in mind that i haven’t done classical music for over 30 years. I was a Bb brass player, (played in the Royal Albert Hall once and twice 
) and this is what i seem to remember (i’ve had two glasses of wine also 
) …
A transposing instrument, like a Bb trumpet, plays Bb when C is written on the scale. So if you got an Eb or Bb whistle you’d have to read the music two semitones below whistle music as that’s written for D whistles. If you get my meaning?
So if you wanted to play whistle music that’s written for D whistle (as in not transposed at all) along with a Bb instrument then they would be playing C on the notes you would be playing D on a D whistle, so you would need a C whistle to play along with them, not a Bb. That’s presuming you’re reading and playing the notation as you would for a D whistle.
For an Eb transposing instrument, you would need an F whistle.
If you’ve learned to read an play music on a C whistle, as it’s written, then you need a Bb whistle to play along with a Bb transposing and Eb for one of those.
As i say, it’s been a while since i did all this nonsense, but i think that’s correct. 
Hope all that makes sense?
If not, try a couple of large glasses of Rioja - that’ll sort it out in your head.
For blues, the minor pentatonic scale will start with xxx xxo (E on D whistle, F on an Eb whistle, etc.), so grab a whistle pitched a step below the key you want to play in. (In practice, this could mean you need several whistles–although there are lots of blues songs in E.)
Here’s a handy thread on blues/jazz whistle: https://forums.chiffandfipple.com/t/playing-blues-jazz-with-the-tinwhistle/76933/1
And blues whistle may not be beyond the pale: http://www.earlyblues.com/featured_article.htm
Food for thought .. thanks to all
Well, you want to have large hands to play a low Bb! Other than that, it is very nice indeed! 
http://music.bracker.co/Whistles/Low_Bb_Whistles
My word … how big is that thing?
It’s got a lovely tone. 
@Beckett: total length 72cm / ca. 28 inches. Bore diameter 26mm / ca. 1 inch.
@free-feet: thanks!
I think I could manage that (I’m 6ft 3in and have proportionally long arms/big hands)
Another addition to the ‘list’
Thanks Hans