Every seller has come across them... the ones that ask silly questions that clearly do not need to be asked if you actually read the listing...the ones that click buy it now and then email you to say they made a mistake or even better the ones that bid and never get in contact.
Unfortunately Ebay do not care too much as non payers do not make Ebay money.. sellers do so Ebay will do nothing about time wasters.
What you can do is make your listing clear.... very clear. Take into account that a lot of buyers are lazy... very lazy and will not actually bother reading all of the listing, so brief and clear is the way to go when creating a listing.
Payment... keep terms plain and simple and stick to them. If you want payment in 5 days and no later then fine - state that in the listing and if someone can not pay on time simply relist the item then after 7 days file a non paying bidder alert.
Set buyer requiremnts too... you can block bidders outside the UK if you do not want to post internationally, you can block bidders who have recently been guilty of non payment or those who do not have a paypal account or no credit card on file etc...
Want immediate payment ? no probs, just use Paypal as a payment option (not great but Ebay insist on it) and select the immediate payment required option. No more non payers...or if you sell bulky stuff then just offer cash on collection and if buyer is a no show after a few days then re-list and file a NPB alert to get your fees back.
also, do not forget the blocked bidder list, you can add time wasters and general idiots to your blocked buyer list to stop them messing you about again.
We had a classic time waster (used id: d-mac-08) who purchased an item via a buy it now listing and then emailed us within 30 mins to say he did not buy it at that price... he wanted to pay 100 pounds less. He clearly had no intention of paying, simple case of an idiot with a PC and too much spare time on his hands.