I'll try to find the link for you mate but I only had a quick look due to being made an offer from MMU and checking where it was in relation to Leeds Met. If I remember rightly the course is offered by 30 or so universities so whilst agreeing not a huge range of choices it still shows ex-polys can rank well.
I do actually think the rankings for the subject you are studying directly is more important than where the overall university ranks but that is solely down to opinion on the matter - same as you will have your own opinion.
Regarding if unis should offer vocational subjects - I personally feel vocational qualifications should be learnt on the job with release to college, similar to that of a trademans apprenticeship. Again, my opinion though. Would save me a lot of debt too ;-). If I had the option of a teaching 'apprenticeship' of university for 4 years I know what I would choose but unfortunately for my chosen career I have to attending university - rightly or wrongly. I'm not here to claim where you study may not make a difference to your prospects post degree (in the private sector) however, like you said, public sector professions IMO are just as likely to hire you regardless of where you graduate from.