I was in roughly the same position when I received my AS grades which were similar to the ones you received. I too contemplated retaking my lower sixth year but didn't. I would suggest continuing onto upper sixth; retaking all the modules you did not do well in. Hopefully you will obtain the grades this time round, however it will take a lot of work.
If after upper sixth you still do not have the grades required, you can take a year out, which is what I did. Try enrolling in a specialist retake college such as Mander Portman Woodward (MPW). They really cram the stuff in and you can take a whole A-level in six months easily.
It will be obvious to admissions offices that you are a retake student and will thus have much higher requirements. This is not terribly detrimental if you attack the situation correctly. At all universities you will have to have grades considerably higher than those stated in the prospectus. For example if they ask for AAA you will need to have AAAAA minimum as a retake student. As regards to your personal statement you will need to have a good reason for why you are a retake student. It doesn't have to be a family illness or anything quite as serious, just tell them the truth. I wrote that I wasn’t very motivated and my interests lay elsewhere in rugby.
There are disadvantages to doing this however, especially when applying to universities other than Oxbridge. LSE does not have an in depth application process, and as a result it isn’t terribly likely that you will be able to explain your self fully to the extent that you stand a chance with regular applicants, though it is possible to obtain a place for the less competitive courses.
When retaking your best shot really lies in Oxbridge. Apply to a college that requires an exam to be taken when you arrive. You want to show the admissions tutor your academic ability. This combined with the correct grades, and a good interview should see you through the process.
Retaking is a gamble, if you do not get accepted by Oxbridge; it is extremely difficult to get into competitive courses at universities such as Lse and Imperial.
Just to give you an idea:
As CDDE
A-Level: ABB
Retake: AAAAAa
Accepted at Oxford,
Rejected at LSE, Durham, Edinburgh