I got BBB and are categorically not resitting, out of principle.
I've never wanted to sell my soul to the magic circle and have always aimed for a high end regional firm in places like Bristol/Manchester/Leeds etc. Although I need to visit more law firms before I apply for the GDL, only visited one so far and was put off massively by the culture inside.
The benefit of the GDL I suppose is that you apply for T/C's after you graduate, logic would have it that the degree would be a better indicator of your ability than A-Levels you sat four years previous. A lot of (high end) law firms will explicitly state that they read applications in full and don't automatically rejected you for not meeting the A-Level requirements so those are ones to keep an eye out for.
Can't really comment on investment banking because it's not an area I've looked into, sorry :P