Im going to buy a Colin Goldie high D. The technical info Ive read on the tuneable ones is a bit daunting. Has anyone any opinions on this ?

I've never heard of his

I've never heard of his whistles -- you'll have to post your results and what you think!

I just received a bit of

I just received a bit of clarification -- Goldie was previously making whistles under the Overton name, so no need to post results -- I'm sure they'll be fantastic! Overton whistles have a long history of quality and consistency and I can only assume that those made with the name Goldie will be just as good.

Goldie makes extremely good

Goldie makes extremely good whistles, I have 6 low tenor soprano whistles and all are perfect. You can also chose big or small bores, color (anodization) or tunable ones.
I discovered Colin by the advice of Brian Finnegan (FLOOK) himself, who uses those whistles.