Looks like people were trying to help you mate, but you only gave them 24 hours!
When you did the oil change, did you not notice if it had a sensor then? I'm pretty sure its quite a hefty plastic part that sits on the underside of the sump, so should be quite easily noticeable - sits over where the big hole is in the picture on the eBay link you posted. If it turns out you don't have a sensor, you're going to have an even more leaky sump when you're done as you'll have nothing to plug the massive hole!
I'd say you got your answer from the lads below, anyway - go and have a look. If you don't have the car available to you, then there's not much else you can do. I'd have said be patient, have a look at the car when you can, maybe even check the part number on the existing sump and then match it up with the new part you want to buy. Tricky, ain't it?
