I wonder if I have too much going on in the left hand that it detracts from the melody ?
I like the left hand accompaniment, and it doesn't seem to me that it gets in the way of the melody at all. What I can't tell from the recording, though, is what kind of balance you're getting. It sounds as if the microphone is placed very close to the right side, so that the left-hand chords sound quite subdued (maybe even a tad too subdued) in comparison. Since your own ears are more or less equidistant from the two sides, your impression of the relative volumes may be more accurate.
On the other hand, concertinas, because of their construction, are unusually tricky this way. I've played in more than one session where I could barely hear myself, only to be told later that mine was the loudest instrument in the room. When you're playing in the harmonic style a listener on your right (like us, in this instance) may hear the melody loud and clear, while one on your left is hearing only loud chords. If you're playing without amplification for a live audience, every one of your listeners is getting a slightly different mix.
When you record yourself, your microphone placement (assuming you're using just one) can be used to optimize the balance. But if you think of recording as an approximation of live performance rather than an end in itself, that strategically placed mic may give a very misleading impression of what most listeners would hear.
I wouldn't change your approach to accompaniment; it's quite lovely. But if it seems to *you* that the chords are obtrusive, you can try playing them with a lighter, more staccato touch. And if you want your recording to give a more faithful impression of what a live listener would hear (assuming s/he isn't next to you on a bench), try facing the mic from a slightly greater distance.