You're always looking for work despite being on ESA and since you so far haven't been successful you're now looking for another constructive way to occupy your time while also improving your chances in future. I have said before that I have a lot of respect for you for trying so hard and you definitely deserve a good break soon, it is s***y in this country however when you're often up against so much red tape. You're one of the minority of people on ESA in the UK that are really trying and a lot more should be done to make life easier for people like yourself, not the opposite and your age shouldn't hold you back from self improvement opportunities like attending college. I would speak to a benefit adviser however as they might have a scheme to help you attend college, but even if they can't at least you will know exactly where you stand.
If you can't easily do a full time college course there are normally loads of adult evening / part time classes available at schools and colleges that are usually subsidised for people on benefits and they're still relatively cheap even for people in full time employment, in fact you may even wish to do a couple of courses if they happen to be on different nights of the week. Basic core skill courses such as Maths, English, reading, writing and sometimes beginners IT are often totally free for people on benefits and cost next to nothing even for people in full time employment (this probably won't be beneficial to yourself, well you can definitely read / write and use a computer). Some courses can actually lead to recognised qualifications, while others are less formal and may just come with a certificate of completion. You can sometimes get a list of classes / courses available from your local council or from one of the venues (well you can in Birmingham, it might be different where you live). I believe many courses start in the new school / college year which is unfortunately in September meaning there could be a long wait. Beforehand in Birmingham there used to be special open evenings at different venues where people can sign up to courses and chat to the various tutors for more information to help them decide which course is best for them (you don't have to attend such an event to sign up to courses however), again it might be different where you live. There are usually some courses that start at different times throughout the year however and even a few that you can join anytime. Many evening school tutors are school or college teachers / tutors that choose to work part time in the evenings to earn extra money.
Best of luck!