As far as i know the minimum reserve you can set on ebay is 50 quid. If that's the reserve and the start bid is 99p and i bid 20 then the auction will be at 99p with one bid. If my first bid was 100 then the auction will go straight to 50 as the reserve has been met by the opening bid. I think it is done that way so a single bid can still win an auction.