I think your to young to be a mature student im sure it is 25 but I may be wrong there is a girl on my course who is 23 she didn't have any qualifications and did an access course at her local college and they accepted this so maybe you could do something like that and apply for next September.
You don't have A-levels but your AS levels may give you enough points to be accepted onto a foundation degree, usually 2 years and they allow you to either go into the final year of a degree or leave with a foundation degree qualification. Not sure if thats the same for all courses and all universities but its what a friend of mine did who didn't get the a-levels they hoped for. You would have to look into it as I am not 100% certain.
Another option if you are hoping to go this September is to go on the ucas website you maybe able to get on a course by going through the clearing process if they have any places left on what you are interested in, think you will have to register with ucas though im not 100% certain but I think you have to go through them. I would do it soon though.
Good Luck
Clare