Buyer wanting to change price

Lauren, no the buyer can not try to negotiate a price after they have won the auction, unless for example there was a fault with the item and they still wanted it, but it's up to you. Auctions are never cancelled as such, but once the success fee comes through you can assume the trade will not be going ahead as the buyer will have either not responded to the Trademe prompt  within 3 days of you applying for the fee refund or has told them it won't be going ahead. I would wait till the success fee refund comes back, then email the buyer to give them 2 days to complete at full price. If no reply or negative reply, blacklist that member, relist the item and place appropriate feedback. 

Thanks for your advice Gary.

There is a fault with the item, however I clearly listed in the description of the auction. They did come back to me after winning the auction asking about it, for which I stated that it was mentioned. I don’t intend on reducing the cost for them.

They mainly want me to reduce the price, due to what they have seen items go for second hand elsewhere. Why do buyers do this! So frustrating, I don’t understand why they even bid.

Yes, if the fault was mentioned then you've done the correct thing. The time to negotiate prices is before bidding, so unless you want it gone, stick to the plan.