The logo on the seat (you can kinda make it out in the 4th pic) seems to be a Haro logo: two downward-pointing arrows with a stylised H beneath. I've found the same two arrows (minus the H) barely visible through the paint on each of the rear dropouts, so it looks like the frame is a Haro of some sort. One of the rear dropouts looks like it might have something else on it too, but it's so faint I'm not sure it's not just quirks in the paint work.

Had a really close look at the rest of the frame, particularly the head tube, seat tube and bottom bracket, and can't see any other markings, at least not that are visible through the paint.

The rest of it's about as much of a mongrel as I thought: Alex rims, Formula hubs, Mongoose crank and chainwheel, and then all the bits I've added or replaced. My guess is the previous owner couldn't afford a brand name ride new, but managed to scrounge one together out of used parts.

Still curious about the frame's year and model. If there's anything I could photograph in higher resolution that would help, please sing out.