What to do about an incorrect GCSE result?

Hi,
I'm now studying my AS levels and all but one of my GCSE results I'm very happy with (4A*s, 6As, 1b). However, one I've had significant trouble with. I went to a terrible high school which was put on special measures in my final year. It was compulsory for me to take a Cambridge Nationals ICT qualification, but let's just say the odds were against us. We never had any good teachers, which lead to nobody really understanding the work or completing the coursework. One unit took us 2 years, we were only informed of the other units 2 weeks before our exams but they somehow expected us to complete them. I worked as hard as I could but wasn't prepared to sacrifice my other GCSE's for something I didn't even know if I was doing right.
On results day we were told that whilst everyone's result was written as an X because the school didn't hand in our coursework, and they were going to try to amend it.
I just received a letter from the school with my 'amended result'. It is an F, and individually I still have the A from the exam, and one coursework unit marked as a C. The other two remain Xs, although I know I completed at least a few mark's worth of work.
I am at a loss as to what to do. I no longer attend the school, so they have no real obligation to me even though I know this is wrong (especially since they have recently been taken over by new management and become an academy). Even if they were kind enough to try to help, I doubt they have my other coursework. They were so disorganised I'm fairly positive they'd have accidentally thrown it out. Plus there is no way I could get a decent grade, a C would be incredibly lucky. I'm not sure if the effort is worth the pay-off.
I would just forget about it, but I'm planning on going to university and I've read that you can't omit any results, and that some top universities discard your application if you have any poor grades. Does anyone have any experience of a similar situation, or any idea what I should do about it?