Hi mailme,
Yes you certainly can do this on a part time (called sessional) basis although I wouldnt describe it as ad hoc, you dont just turn up when you like!! At the least youd be expected to take on a module of some sort.
You havent necessarily missed out on this year - there maybe specialist units (such as a project management module within a broader management course) that dont kick in till later in the academic year.
Also you dont necessarily need an adult teaching qualification right now although will be expected to show willing to getting one at some point although thats relevant for a longer term commitment. You also dont need to have taught previously or no-one would ever get into it, but you should be able to say what elements of your full time role have given you experience of communicating with groups of adults. If you have no experience of this you shouldnt really think about teaching just yet, students are there to learn not be your guinea pigs!!
You will need to work from your qualifications. You are nowhere near qualified or experienced enough to teach business analysis to adults in FE. Prince wont be enough without a management qualification which leaves us with multimedia which is where you have most chance of success. I hope your BSc is a 2:1 or above, if so this suggests you might teach up to HND level which puts you in the FE college arena so look on the vacancy pages of your local colleges. Prisons also use sesional lecturers.
You will need a lucky break to make this work, why not think about doing the first stage of an adult teaching qualification instead? You might be able to get work to pay for it, it will be useful in your job, and the college can help you get a placement to get your teaching practice (although you almost certianly wont get paid). But youll have a qualification and thereby have easier access in future, and you will have established whether it