Do ya BA.
In third year, apply for GDL.
Complete GDL over a year (or thereabouts). Normally it's the new unis which offer it. You don't do the GDL for prestige; ya just tick a box.
You can get firm funding prospectively and retrospetively. So you can apply for TC in third year of BA, and then a firm will pay for GDL. Or you could do GDL, later get the TC; and firms will pay for the GDL fees you forked out. Most firms won't pay for the GDL, though.
HOWEVER The SQE will make the GDL redundant in the next couple of years for aspiring solicitors. Currently the LLB (or the GDL) pass the academic stage, but with the SQE each student will have to pass the SQE1 to pass the academic stage. Passing your LLB or GDL won't be enough. So in theory, you could do the BA and then not do another course after -- instead self-teach the SQE1 prep.