Just S.graminifolium I think Luke, we are not so high that it would be out of the question. S.montanum has a more compact rosette and is found higher up in the landscape.
All about morphology (not indirect cheap ID tricks like altitude measurements) and habitat of especially soil type (whether weather wet or droughted in the current climate. If the soil is peat including past wet climate formed peat in a nowadays dry area. ). Plants respond in their terms (not to humans' terms per se such as of measurements of altimeters). @Tapirlord I hope you've done some plants' species distribution modelling in your uni. studies . I refer to the last 30+ years of CSIRO SE. Au. plants species distribution modelling, notably Mike Austin .
Please refer to information i have added in to these species pages here : Stylidium montanum – including regarding leaves' serrations . Not serrated at base .
Quotation: " ...
Leaves linear to narrowly oblanceolate, greater than 3 mm wide, pale to dark green, serrations absent or towards apex only, lamina continuous over midrib and leaves not bifurrowed; flowers pink to deep magenta – 2
2. Leaves 4–15 cm long, pale to mid-green, widely spreading to suberect; scape fine (< 2 mm wide), glabrous or glabrescent below lowest flowers; flowers 10–30; in water-retentive, peaty soils of montane to subalpine areas at high altitudes – S. montanum ... " .
Especially refer to the fifth (and also fourth) of the photographs here – at full resolution .