Since you can't attend a brick university because of money, you could study with the Open University (part-time, if you're too tired after work... and I get that, I've been there!!!).
I studied one year with the Open University before transferring to my current brick university, but I miss it so much and I cry all the time when I think about this massive mistake I made.
The Open University is very good... you can try to study Computing & IT (I actually studied Python in my first year at the OU).
Also, why doesn't your gf contributre to the rent?
I wouldn't really live with someone that doesn't work and contribute, unless they can't work due to disability or illnesses...