Thanks guys for getting back to me with many ideas, it seems there is a lot more to consider than I had first thought of so I will explain a bit more about what I'm after and what I want to do. At the moment I have an onza zoot which I am thoroughly enjoying playing.
Aswell as what is best described as a hardtail freeride bike, a fairly long, very stable bike that is most at home riding off/down sketchy constructions in the woods. Its an old school huck bike and good one too in that it is very forgiving. Unfortunately I am getting too old and wise to use it like this, and as it is it needs atleast a new frame/forks to be re purposed to anything else other than a very heavy xc bike.
Back to the present, though I am just learning trials I am seeing plenty of lines that would be a lot of fun, yet a bit sketchy on my zoot (Often things involving stair sets), so I'm considering re purposing my current mtb into something trialsy enough to preform the basics and allow me to access some new lines without taxing my limited skill base too much, and still being capable of the odd slow trip to the woods.
The inspired hex, and custom builds seem like good matches but a bit on the pricey side for me. I am expecting the best match I will find will be a street/freeride orientated frame that will not feel too out of place with a 90mm stem. As for fork length, I will probably seek out a mid weight rockshox fork with u-turn and play around with fork heights to get a good compromise before looking for a more solid/reliable fork, I have found some frames are exceedingly good fun with shorter than intended forks, but also many others that aren't. I am weary of the old school frames recommended on account of metal fatigue, though they do look like great matches for me.
What I might well do is look up the geometries of the frames mentioned and seek out something modern that is similar, though ultimately my experience in trials is effectively zero so I don't really know how a frame should feel riding it and will rely on your opinions to make sure I don't end up with something too unsuitable.