It's not too late for a GDL, but you may find that it's too late for a career in law - after the GDL you'll still need to do an LPC / BPTC, followed by a training contract / pupillage. You may very well find that employers are not keen on investing in the training of someone with relatively few years of working life left in them, when they are swamped by other good applicants.
I would strongly suggest that you talk to some firms that offer training contracts and pupillages so as to get the lie of the land.