Actual registration at the time is also shown on MOT certificates. I've never looked it up on the electronic records but imagine it would show there too.
Previous VRM's will not show on a V5/V5C, the best way of seeing a vehicles ' previous ' vrm is through HPI or Experian Autocheck report which tells you when the plate was removed and what vehicle its now on if any.
yes an HPI or Experian report will show any previous VRM that has been legitimately on the vehicle/chassis in its life. As a business we use Experian Autocheck via our account, but have used HPI in the past but both supply pretty much the same info but in a different layout.