So you've completed a 3 year degree course at St Martins, wern't happy with the outcome, and want to do another degree course? That's commitment. Can't say I'd do that. If location is no issue, I'd recommend the graphic design course ran by Weston College in partnership with Bath Spa University.
I graduated from there 2 years ago. I did their 2 year FdA (Foundation Degree) Graphic Design course, and a 3rd year top-up to a full degree.
I originally applied to Falmouth, Plymouth, Camberwell, and Bath Spa/Weston. I got offers from all 4. Falmouth's reputation is awesome, but the people there were so up themselves, and the facilities (at least when I was there) were awful. Camberwell accepted me, on the provision that by the time I started, my parents were earning more than when I was interviewed (snobby bastards).
Bath/Weston's course blew me away. Not only was there at least 4 hours of tutor/student contact A DAY (that's so unheard of at university level), each student had their own desk space, a weekly tutorial as well as brand new facilities.
Most 3 year degree courses don't offer alot in experience or focus after graduation. The most you'll find is probably outside speakers, some print workshops etc.. The Fda/topup was so different, and so much better. Instead of a regular 3 year university degree where not a lot happens after it, the 3rd year top-up was solely focused on life in the industry after. At the beginning of the 3rd year, I actually began my own design studio with 2 friends on the same course - whilst studying. This gave us 1 year's industry experience before we'd even graduated. We had business modules, freelancing modules, networking modules, as well as guest speakers, the lot. We were running our studio whilst writing our dissertations too. I don't know of many other uni's that offer this sort of thing.
Whilst some uni's have good reputations, there is no way I'd be where I am if I had started at Falmouth or Camberwell. I'd definately go for an FdA degree and top it up after if you wish.