The Bosch Car Service OFT approval differs from the other schemes in that it is actually very closely monitored by Bosch.
Bosch are conscious that their branding should not be used anywhere where it could bring them into disrepute with the buying public. Hence their very strict criteria and the OFT approval, which incidentally was hard won and granted in stages.
From what I have seen and read, I don't think that the Motor Codes scheme comes close to the standards that Bosch Car Service set and maintain in their network.