Just wondering why you wouldn't want to work in Engineering? I think you will find general office/ managerial work even less exciting than engineering. At graduate level most engineering jobs are based in research or design/development (apologies for the generalistion) and will be still mainly office based. You should know that in terms of maintenance type jobs then that is a separate stream of training traditionally based around an HND level of qualification and requires study for the CAA (assume EASA now) licensed engineers exams, normally this route is entered via an apprentice type scheme; not generally an area where a graduate would start their career (I do not mean this in an elitist sense, studying for the CAA Eng licensed exams is not an easy process and just as academically challenging as a degree).
I must admit when I finished my engineering degree, jobs in engineering never really appealed to me, however although starting salaries for graduate engineers are not particularly brilliant, it is obvious that you haven't checked out contract rates for engineering.
Get your self 2 to 3 years engineering experience in the avionics field (consider going into reliability or safety these have good contract potential), you won't necessarily save alot in this time, but you will gain the credit rating to borrow to do the training whichever route you choose. (Infact with an avionics degree you may be able to get into an airline engineering department doing reliability analysis).
After your training with three years eng experience you should be able to go back to the industry as a contractor earning between £25 to £35 an hour. Hence be able to clear your debts in a few years rather than a decade. The avionics/electronics sector is generally short of engineers which means it should be possible to get into contracting with relatively low experience (traditionally most contract agencies require 5 yrs experience).