Thanks once again folks for all your replies and insight. The consensus is that I am on to something, the verses are good, but the chorus is a little underwhelming and the crunching rhythm guitar should perhaps persist throughout. I was never sure about the synth sound.
I am going to attempt what I never try to do, and surgically change it - keep the verses as they are, keep the lead guitar, ditch the keyboards, and rewrite the chorus melody and structure.
This is much harder for me than writing a new song from scratch, but I feel the core of this song is quite good, and I want to give it a go.