Robert,
I originally trained as an engineer and did an Executive MBA at a 'red brick' university after 15 years in the aerospace industry (2006). Apart from the networking opportunities and the experience of being back at uni, I didn't really learn anything of substance that I hadn't already figured out. My experience is that many graduate engineers become managers as a virtue of their role with some developing good management traits whilst others lack even the most basic social skills. But this is no different to almost any profession!
I found the MBA to be the application of common sense wrapped in a little business jargon and bound in books. I have no doubt that it opens a few employment doors but if you are pitching yourself at MBA level employment, the likelihood is that you will be more successful by networking or being head-hunted. Spend £20 on an MBA overview book at WH Smiths and see if this is what you want before you enrol. I was on a course with a mixed cohort of engineers, doctors, public sector high-flyers (no pun) and a few directors - all 3 of the engineers were bored throughout apart from the maths within the accounting and finance module (sad I know).
Would I do it again if I could go back? Probably not. I would likely undertake an MSc. Little use now as I have moved to the dark side and decided to fly instead of fix. Good luck with your decision...