I'm off to Westbury in a few weeks and am also doing the 'challenge' in July to do phase 1 in 5 weeks.
At what point are people classed as 'Potential Officers'? When do you cease to be a Pvt and become a PO?
From my understanding, PO is what you are once you decide to go the Officer training route, it means nothing and is just an expression of interest. However re: your unit I'd still call yourself a Pte. (Sig, Spr, etc.) until you've done AOSB Main Board, at which case you officially become an OCdt. PO is a very wishy washy thing imho.
More than willing to be completely and utterly corrected on this one mind!