Callum, if seller does not put a cash option up not wanting to use ping, there's no way of bidding anyway with limited options or even contacting to purchasing a item. If a bid is placed i don't think he can change description so you a buggered. Some sellers don't want pick ups even if had no plans to do such ..   

I personally will not be using ping ever so it will be just local pick ups i will bid on if the seller allows it via cash only, i have already told old clients not to store and will not bid on future items to be paid for by ping. After 30 odd ys of Trade me its very disappointing to see the stupidity of this.. Never had a issue other than a odd post delivery. So all you sellers far away, i'm sorry but thxs for past service. On course i will not be selling either as they will force me to use ping just like ebay with p/pal.