Bureaucracy Gone Mad

Allowing cyclists on some of the streets off Mill Road to cycle both ways on roads that are one-way for drivers is a controversial issue. Personally, I think there is a huge benefit to cyclists in speeding up journeys like this with little or no increased risk or invconvenience to other road users, so I support the changes recently introduced to allow two way cycling. What is indefensible however is the way the Government Department of Transport insists on very specific forms of signage to allow this, which actually cause problems because they won't allow a simple arrangement that makes it very clear that the roads are only one-way for cars. The following is a good suggestion for how two-way cycling should be allowed:

But some bureaucrats sitting in an office in London don't like this, and according to the police, this is causing problems with some motorists ignoring the no motor vehicles signs (the "flying motorbike" sign) that have just replaced the no entry signs to implement the new policy of allowing two way cycling. I thought I would ask why...

To: Traffic Signs dept, Department for Transport
Dear Sir,
Here in Cambridge cycling is a significant form of local transport, that makes a huge contribution to reducing congestion and promoting sustainable travel, so as a local Councillor I am keen to promotecycling as much as possible.
One way of doing this is to permit cyclists to cycle both ways down a street that is one-way for other traffic. A very simple way of permitting this would be a form of signage that makes it clear that aroad is no entry for vehicles except cyclists, along with some simple road markings at the entrance to the road. (See attached picture).
However, I understand that due to Department for Transport rules, this form of signage is not permitted, and either a less clear form of signage or over-engineered street works are required to make such asimple change. (perhttp://www.dft.gov.uk/pgr/roads/tpm/tal/cyclefacilities/contraflowcycling?page=3#a1004)
Contrary to the comment in the guidance ("At the sites monitored by TRL, compliance with this sign was found to be good."), I would like to provide feedback on how replacing no entry signs with no motor vehicles signs (per figure 2 on the guidance page linked above) is working in practice on several roads in Cambridge with signage recently changed. The police have reported to local Councillors that this has resulted in numerous car drivers believing that the roads inquestion are no longer no-entry for them, resulting in cars travelling in an unexpected direction on the roads in question, and requiring an additional police presence.
Therefore, could you please let me know:
Is the form of signage proposed in the attached diagram actually prohibited? (i.e. is the 'guidance' mandatory)
If it is not permitted, why is this?
Can this form of signage please be permitted?
If no, what form of legislation or edict from an elected person/minister etc would be required to make such signage permitted?

UPDATE: I should point out that Cambridge Cycling Campaign have been campaigning on this issue for a while, and have a much better explanation of the problem here.