[CorsaModder]

I've got a 2001 Corsa C which I use mostly to go to and from work every weekday and a few other places too. I don't exactly cover a great distance approx 87 miles in a typical week but I've found that I go through about 1/4 tank of fuel a week. I worked out my MPG and it's shockingly low and I'd like to see how I could improve it (bearing in mind that it's a 8 year old car, although well cared for, and I'm not exactly a mechanic). Does anyone have any ideas of where I should start? It had a new set of tyres installed a few months ago at the cost of, I think, £230 (I don't know anything about them but apparently they're decent) so would rather not do anything there.

Looking at the list of possible mods I think the following might be realistic:

Solar assist - solar panel on roof that trickle charges battery. Unfortunately I don't think I'd ever get enough back to make the cost of the solar panel worth it however much I might like to do it. Also it'd probably get nicked or vandalised.
Weight reduction - I've been thinking of taking the back seats out as they're pretty easy to remove and when I do have passengers I never usually have more than one so they'll sit in the front driver's seat. I've also thought about replacing the 2 front ones with racing seats but I don't know if it'll be worth it from a weight point of view or if it'll require changes to the seat belts?
Aftermarket cruise control and setting the cruise control to control the throttle via engine load rather than speed. I don't know if I can get aftermarket cruise control for my car-couldn't find anything on Google-it's a pretty basic model but it's something that I might be interested in.