A CPE is more than sufficient for practice at the Bar, there is no need to take a law degree especially considering the age you will be when you are ready to re-commence study. If your sole aim is to practice rather than to appreciate law from a broader and deeper level then a CPE rather than a law degree will be more appropriate. You will find that numerous barristers have taken this route with degrees as variable from classics to medicine. Indeed your medical qualifications will be particularly marketable to any chambers specialising in professional negligence/clinical negligence, or with IP sets (which generally seem to favour those with a science background). If you do decide to go down the law degree route it would be advisable to take the senior status route rather than the traditional undergraduate three year course, since it is one year shorter.
Is your intercalculated degree classified, even if your M.B., B.Ch., isn’t? Even if not the problem should not be too great provided your marks are comparable to what would otherwise be the required classifications, but contact the relevant law schools to be sure.
Generally for transfer students into law it doesn't matter too greatly where you take the CPE, but for the Bar there seems to be a distinct bias towards City University, especially at the leading sets. This may be the fact that they use lecturers from highly regarded Universities. It would appear that despite this where you read for your undergraduate degree is still considered highly relevant, although if you are applying from the position of a practicing doctor this may not be applied to you so greatly.