re send it back:
additional equipment would help big time. the hiss in the background is too distracting. maybe you could try noise reduction.
but let's say the acquisiton of additional equipment is out of the question. i think you can imporve the vocal sound by cutting some low frequencies, or perhaps singing a little farther from the mic to reduce proximity effect. the guitar sounds ok
you might try doubling the parts, using different presets, then panning the parts hard left and hard right just to get that stereo effect. your music reminds me of blur, which is a lucky thing because brit rock usually use drum sounds that are more natural and roomy. this shouldn't be very difficult to get with minimum equipment.
also when the music changes in amplitude (or gets louder) you have to automate the vocals, raise it and bring it down appropriately so that the listener does not strain to hear what youre trying to say.
your song is quite nice actually. you have to bear in mind that live arrangements usually differ from recording arrangements. when you arrange a song for recording, you have to consider panning, tone (EQ), etc. try listening to commercially released albums (blur for example)to get an idea of how recording arrangement is employed. you can really exploit the left and right channels to your advantage as your song have overlapping guitar parts moving from one portion to the next. the element of surprise is a nice thing to use in a song
good luck and congratulations on your first try.
