Well, I love this tune, so kudos for even doing it.
But, what everyone is referring to as "harmonies" aren't even harmonies. They're just an octave apart, which isn't in the original. I'm not saying that's "wrong" if it's your own take on it, but it has nothing to do with Dr. Hook's version of the song.
Also, until the first chord change, you're not singing it in the right key, or a better way of putting is that you're both singing a harmony to what the lead vocal should be, if you know what I mean. Once you hit the chord change and say "Sylvia's mother says Sylvia's happy, so why don't you leave her alone", that's the only time you're actually singing the same part as the original. Listen to the original and you'll hear what I mean.
To be more clear, the first note of the song should be a C#, you guys are singing an E. It's not the wrong key, but it's the wrong "position" or "harmony", for lack of a better word. (The chord is an A major)
Besides that, reverb, no reverb, whatever, that's personal taste. But get the parts right is what concerns me more.