In order to make an informed decision you need information that will allow you to distinguish which outcome, for a given course of action, is more probable. In the absence of that information it doesn't makes sense to invest tens of thousands of pounds and years of time in something where the only thing you're really sure of is you're going to be bored to tears by it.
As an adult who is currently going back to school, I would have to say that the decision should be based on your desire for a final outcome. There are plenty of jobs that don't require a degree, just a passion for the field. And there are jobs that require a degree. I see too many people in school now who are just going back because they have no idea what else to do. That is a huge waste of money. If you don't have an answer as to what field you plan to be working in and why a degree is necessary in that field, you probably shouldn't be in school. I'm not sure what the education costs are like in England, but I will have spent about 75k by the time I finish my undergraduate degree, and I will also need a Masters on top of that. I have a good understanding of what I will be making when I get out of school and the kind of job that I will be doing. Without that understanding, well.. 75,000 dollars is a LOT of money and 4 years of your life is a LOT of time that are both going to waste.