For those that are interested, here is how it panned out!

The item in question was a Macbook Pro - pretty high spec.

I was going to remove the bid of the "suspicious" bidder and then block them, but before I did so, I had a number of higher bids from well verified and long-serving users, so I let it lie - though had this trader then put any higher bids in, I would have removed them.

In the end, I got a very satisfying price from a veteran Trader who was lovely to deal with and it all went off without a hitch and I didn't see anything more from Mr/Mrs Suspect.

2 days after, I got a direct "security warning" email from TradeMe, warning me that an (undisclosed) bidder had viewed and bidded on one of my items and had been subsequently identified by TradeMe as dodgy. I was warned that they may try to initiate direct contact, bypass the Auction process and try to defraud me. This was pretty much in line with my experience and suspicions and when I checked, Lo and Behold! That user had been deleted and all their bid history had vanished.

So yes, us suspicious types on the thread were right to be so!

Thanks for the input and advice.