If you can get a competitive GMAT score on the retake (680+, ideally 720 or more), then by all means shoot for LBS. Also, in addition to Cass you want to look into Oxford and Cambridge - schools that are somewhere in between LBS and Cass in terms of overall reputation and schools where you should be competitive for.
Alex, Thanks a lot for your reply. That certainly has given me the confidence and the motivation to strive for a great GMAT score. will surely keep you posted on this. I am due to give GMAT on 12th December.