I don't think that is a particularly sensible question to ask. I know there are many anecdotes recording that, historically, the UoL external LLB awarded very few firsts and 2:1s, but (even assuming that there is some statistical truth in that) that does not imply that any given student will find it more difficult to get a 2:1 on the UoL course than on the BPP external course (or any other course). The low numbers of firsts and 2:1s may just be due to the calibre of the students that enrol rather than to any overly harsh marking.
I suspect that the 2:1 from BPP would stand you in better stead than a 2:2 from UoL, but not by much and I suspect that neither result is going to be looked on particularly favourably by employers.
I suggest that you work on your English as from the evidence I have seen you are going to struggle with an LLB. (I have had due regard to the fact that no-one writes as carefully on a forum as they would on a job application or a piece of coursework).