The UCL website states you need grade 6 in GCSE English Language and Maths to be eligible for medicine, so no, you don't meet the entry requirements for studying medicine at UCL. Therefore, yes, if you wish to apply there you must retake. The same goes for KCL, St George's and QMUL (Barts). Imperial does not have any GCSE requirements.
Either you retake, or you change where you want to apply, and/or consider the viability of applying to medicine at all.