@Phil M.
It's always a good idea to put in your listsing what time scale you want paying by.
I do a fair bit of buying and selling on ebay, and in mine I always put: Item to be paid for withing seven (7) days of auction end.
That way, you're giving them a bit of leeway in case they havent got the reddies that day, or a few days to transfere money between accounts etc. but not enough time for them to start taking the piss.
If they don't pay within the seven days, I send a reminder on the seventh day, with a further 48 hours.
If then they don't pay, you just open a case or relist the item.
If they say they require a bit more time for X, Y, or Z, then I'll usually accomodate them for a bit longer as long as I'm being kept informed.
There's nothing worse than someone buying one of your items and then you hear nothing.
In shorts, It's always advisable to give people areasonable length of time to pay, as long as A. You're kept informed, and B. it doesn't start dragging on for weeks.
As an example I had a lad buy something off me a few years ago, and the auction ended about three hours before he was due to board a plane for his holidays. He got in touch straight away and explained the situation, and I waited for three weeks to get paid. Fair enough.
Another pointer, as pointed out, is people with very low ( mainly single figures) feedback.
Most are genuine, but it should still keep you on your toes, and make you ultra suspicious. Moreso if you are sending the item outside of the country, as the Police can only track and deal with fraud within our own borders.
If sending things abroad, insist on over the top postage costs to cover it being tracked and or signed for at the other end.
That may not neccessarily stop any fraud, but it will in most cases cover you with ebay/paypal if you get ripped off, and they'll usually refund you when you prove to them you've taken all availabe steps to stop any bogus buyers.
If you need any advice, just PM me.