Sorry to put a slight downer on it, Criminology has become incredibly popular across all types of institutions, but there are not enough jobs in this sector of the type people imagine they might get. For example, many people would like to be a CSI, but usually the police train in-house, from those without degrees, leaving all those people with firsts in Criminology wandering around. If you want to work in social work or youth work, I would probably do either a tailored social work degree or a solid conventional 'academic' subject (e.g. Psychology).
Doing Criminology isn't valueless, it's a great subject, but it's also a fashionable subject and there are thousands of graduates wandering around with Criminology degrees (or that with Psychology, Sociology, Social Policy) who can't work in the criminal justice system. It is a bit like law: it's not that no-one gets jobs, but they tend to go to the best universities and/or work very hard to get contacts in the area from which they launch their further training.
I don't want to be discouraging, but sitting in a small town, without making contacts, without really having a focused goal, slogging for 6 years plus at this particular topic to get an OU degree may not give you the type of job you want. You may be better off doing social care/youth work type work now, and working your way up to management/strategic level.
I teach a social science subject at university, and without a doubt, the students who really make the most of it are the ones who are massively proactive outside their academic studies, they usually end up with a 2:1, but a list of contacts/companies/very strong focus on what they want to do. And many professional jobs (e.g. working in consultancies, researching, consumer/retail sector) expect a Masters as well, as a minimum.
I would pick a subject which is solid academically, and which you are really going to enjoy (so get better grades), then spend a good proportion of your time making contacts/doing placements/contacting local businesses/charities etc in pursuit of the job you would like to have once you finish (focus on this rather than just getting a degree).