First, I apologise if using that photo was not appropriate! Seeing the good side of it, it does not say anywhere they are your plants, just your photo ;) And in fact I found it with much better colours than old photos here of the many horrible looking eucalypt plants I have grown along time until learning some of the good things :)

Re the gunnii/archeri, it is difficult to find out which is it at this stage, but I think it is a good guess. We could compare samples of those leaves with samples of clearly known examples of each type of these "gunniish" eucalypts, and observe bark. Flower buds of capsules surely give better hints, but the plant is too young yet.

Still, in my opinion, any of both subspecies do have a quite similar behaviour in cold temperate areas, and their apparent difference in cold hardiness is not that important (effects of microclimate matter more!).

The good news is: no mattter which E. gunnii subspecies you have, with that plant size it will re-sprout after being coppiced (and transplanted to a bigger pot, and/or rootpruned). I am quite sure those plants have a lignotuber already, but maybe a bit buried with potting mix :) (And if it did not have a clearly visible one, it still can coppice, they are vigorous re-sprouting eucalypts).