You note the demise of the MMB and the races ‘morph’ into Kelloggs / Pru-Tour / ToB – however, there was little of the Milk Race that passed into these new races.

One key fact missed from your assumptions was the rising costs of promoting such a race – specifically policing costs – and not a little resistance (even hatred of) cycle events within parts of the police service. Some county forces would move heaven and earth to prevent the race coming to the county. The opportunity presented by the rise of ‘health and safety’ and the ability to charge for a wider range of policing services saw two changes.
1) The formation of an ACPO Escort Group (allegedly cheaper – for individual forces yes but not service users)
2) Rise in cost of policing – from a few 10′s thousands of pounds to several hundreds. No alternatives were available then and so this was ringing the changes that was then seen as being the start of the demise of the Milk Race and domestic road racing. A position that still remains today – with the exception of a few dedicated individuals on the NEG providing some service to high end races.