Why isn't it offered? The answer from numerous professors is essentially the same - they don't see the benefit for their universities compared to the considerable effort required to create all of the distance learning material.
I'd not personally discount OU's
BEng and MEng products - whilst they are a bit more general than one might prefer to see, they're real grown-up degrees, which appear to meet ECUK requirements for accreditation as an Incorporated or Chartered Engineer through some institutions, and also have a reasonable amount of internal flexibility for you to direct your studies in the way you want to take your career. In my opinion, most employers will probably treat an BEng or MEng degree as equivalent to that from most other UK Universities and so long as you picked your modules sensibly and don't mind a bit of self-justification, CEng through IMechE or RAeS is almost certainly achievable.
Embry-Riddle is a well regarded American teaching only university which specialises in correspondence courses. In the UK, it's degrees are not all that well known, but reasonably well regarded amongst those who have bothered to look. Its biggest weakness is that it's not a PhD granting institution, which both in the UK and the US makes it "second tier" because its teachers are not active in research - the OU doesn't have this problem, its academics are very active and an OU PhD is a well regarded research qualification.
If you are looking at this to enhance your RN career, then there might be an option for you. I understand that there's a deal between the Navy and Southampton University for prospective officers to do an engineering degree there. The deal seems to be along the lines of agree to serve for a minimum time after graduating, released for 3 years to study, and if you pass you get a full commission, if you don't you've got a lot of explaining to do! If this fits in with your plans I'd recommend having a go - Southampton is a world class university offering good aero, marine and mechanical engineering degrees, there are a lot of Naval students there so you'll fit in, and it's a nice spot to live and work. The best way to find out about this is probably through the Navy itself. (There's also an RNU unit, HMS Blazer, which is Archer class attached to the university.)
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