Listed a multiple item (three items in all) BIN auction on eBay last week. Within a day and after midnight someone has bought two of them. Didn't pay though. So I send them an Invoice the next day. Three days go past and not heard anything from them. I have set as one of my t&c's that sellers need to pay or verify payment type within three days of sale.

So I send them an e-mail last night saying that I haven't received payment or details of how they are going to pay. I also said that if I don't hear from them by Monday I'll report them.

Got an e-mail this afternoon saying 'Don't know why these are in my bought section. Didn't bid on them etc…'. Very polite but complete fiction.

I have no issue with people changing their mind after they purchase. At the end of the day people make mistakes but don't lie about it.

I'm in two minds at the moment. Do I persue an 'Unpaid Item' dispute or do I just cancel the sale and leave the buyer to mess about other Sellers.

Pursue the unpaid item to get your fees back, you can't buy without confirming your password so either he's lieing or someone else knows his password, neither are your fault

my account has been used to "buy" form ebay by 3rd parties – ebay denied the transactions

What do you mean 'eBay denied the transactions'?

They emailed me and explained that they thought some unauthorised activity had taken place and advised me to change password. They canceled the "purchase"

I had this about a month ago, selling an mp3 player. It seemed to me as though the 'buyer' was bidding me out of the market because it my selling price was competitive. Anyway, that bidder 'won' but didn't pay. I second-offered it to the next highest bidder who didn't answer. So I complained to ebay who didn't respond, so relisted, sold it for £30 less than the original 'won' bids. Feckers.